Thats some good info. Must say I should have read the first post better, thought the canards were brake ducts and it was just about the front lip design.
After realising that, I wouldn't recommend canards themselves, for questionable legality and their complex interaction with your current aero. But I still maintain that you can definitely improve things.
Having a rake on the floor is the same principle as a diffuser. A constant amount of air is flowing under the car, but the space it fills gets bigger towards the back, so pressure drops and the car gets sucked onto the road. Using proper diffuser channels allows you to adjust the Centre of Pressure, so you can balance the downforce. Hell, you could probably design one of these using empirical data, they are quite simple. I think I may still have the data from some wind tunnel testing I did at uni.
 
Another project I have in mind is an Exige style engine cover. From what I've read the notchback style is really terrible for drag.

Sounds like you lot all have a degree in aero lol
Bossman Admin has 2 canards on the front of each side of his beast. 
Madpsi also stocks a rear diffuser for the SW20. Anyone know where we can get flat underbody panels? Or is that something people usually just make themselves?

WOW!!!!

This great info. The articles I have read lately have been talking about balancing aero front and rear but how do you do this with out CFD Modeling, a wind tunnel and degree? Test and measure on the track I guess?

Car is for sale for 2 more weeks. If no one buys it I am throwing more time $ money at it.

The car has a large front splitter that was fitted with a couple of bolts to the front bar by the previous owner.
I braced the splitter directly to charis I noticed a big improvement, but I would like to make a smaller splitter for it. Are there any designs that seem to work better? Or anything I should consider in the new design?

It did have an aluminum double bladed wing that is semi adjustable so I might put it back on the car and have a play

Would you recommend buying some speed flaps?

I would like to design and build a rear defused similar to the Ferrari 599xx. Is there anything I should consider?

I will also be designing and building a rear engine cover similar to exige or Ferrari F40 I have a couple of concepts in mind.

I might look at the prospect of an under body tray at the same time.

If I did design and build this stuff would it be worth moulding them? would anyone be interested in buying this kind of stuff?

Looks like I am going to be busy for a while???

Depends on how it turns out if people will be interested. Ive considered on doing similar stuff/ would buy if the quality is right.
 

Ild rather just see the results than to read on the subject.
 
And see them i have with my engine builders track car.
 
It has literally 1000's of hrs of testing even with his home made/dyno wind tunnel.
Hard to believe but the results are better than any Ferrari

Real world testing is always the best idea if you can do it. CFD is useless unless you can validate it against something accurate, and even wind tunnels aren't perfect unless you have a rolling road within it.
For measuring downforce, I've used linear potentiometers mounted on the shocks to measure the suspension travel. So go drive 100kmh with and without your aero, and you should have a difference. However that was with downforce of around 10-15% of the static weight, which you won't get close to on a road car, so dunno whether it would be accurate enough.
Alternatively you can use strain gauges/load cells on the mounts to directly measure how much force its pulling down with.
 
For drag, if you can log speed data (electric speedo, ABS sensor) then its really easy to measure with a coast down test. Again start at 100kmh, then just let the car drop speed on its own (in neutral). The drag force will be equivalent to your velocity^2, whilst rolling resistance is only equivalent to the velocity. Some quick maths will give you the drag coefficient, so you can test whether it changes much.
 
I believe EMS powered sell the flat underbody panels, but they're aluminium. Not the material I'd use.

blacky83, i'm guessing you did mech engineering or aero at uni, and did formula sae?? Linear shock pots are awesome if you have them available to you, but can be very expensive. I use delco ride height sensors off holdens with hid's, with a small 3/16 link to the lower control arm. There isn't a lot wrong with using alloy for undertrays, it is a bit heavy, and it has to be braced, the thing that you need to keep in mind is whatever you use, it has to be rigid to ensure that the airflow stays attached to remain effective. Steep angles are to be avoided for this reason. Small diffusers in front of the front wheels can be quiet effective, with some small strakes mounted to them. When doing front splitters, you must keep in mind that the further they protrude, the more leverage they have. For the coast down test, you only need to coast down 10-15km/h to get enough data, and note that one you attempt the test above 150km/h, drivetrain drag increases exponentially. If your getting to the point of using shock pots and doing coast down and constand speed tests, you will need to invest in some form of weather station to help eliminate some variables of windspeed and direction, as piezo tubes are over the top for a road car. Also with an mr2, if you make a front splitter and extend it under the front between the wheels, make sure you don't seal it to the body too much, or if you do, consider how you are going to get the air out once it has past through the radiator.

I'd be interested in buying if you make it :)
My under panels aren't in the best shape anyways... 

EssDub and I were interested in getting some new front panels made up too (maybe CF?). The two small ones underneath the radiator.

Yep, I was involved in the Uni of Adelaide FSAE team for a bit. Was a fantastic experience, and it was really nice having so many resources to work with. There would be race teams with less access to some of the things we were using, only most of it we had to teach ourselves how to use.
Linear pots are pretty expensive, unless you could borrow a set. Alternatively it should be possible to rig a rotary pot to measure linear displacement, though it would need to be calibrated. I'm not familiar with the Delco sensors, how do they function?
 
Aluminium floor wouldn't be as heavy as I originally thought, but I still think for something that is only really supporting itself, you can get away with something a lot lighter. Fibreglass or carbon fibre are pretty good if you are able to work with them. Otherwise you can get sheets of aluminium/foam sandwich board pre made, or even corrugated plastic lke Coroplast. As for the radiator, ideally I'd like to use a vented bonnet and route the air upwards (this can also help with downforce, marginally) but I think this requires cutting of the body.