Little worried that none of those swing back to the rear engine mount for a better support structure.


 
Mine I'm not a fan of those small bolts taking a lot of the load, I want to look at upgrading it to a bigger bolt or shoulder bolt.

I want to upgrade the mounting bolts from the current little M12 to a much more suitable M16 in a 12.9 grade, then replace the solid brace from the bar to the rear engine mount with a 40x40x5 tube section frame with some addition braces towards each towing mount point. It might be a little over the top, but I'd rather it be a little heavier and safer then anything else.

bnicho, that Draw-Tite one utilises factory mounting holes which have a nut attached to the backside for the top holes.
The lower holes (pictured with grey nut bracket thingies) require removal of two 10mm rear bumper bolts, drilling out the hole to 12mm and then bolting through (into the nut brackets). The metal bumper support bar also needs to be trimmed in the centre. This cannot be seen from behind the car though. 

Thanks for the pics knightrous.
 
Here is the installation guide for the Watling one. It appears to be braced to the engine mount also.

Sweet! Would your design work for both N/A & SC bodied cars? Early N/A as well?
 
Are you seriously thinking of having your design built?

That's a decent price for a brand new towbar. Doesn't look like it has the crossbar though?
 
Knightrous; My GT's towbar bolted onto the chassis rails using 2x M12 bolts at either side, and that's rated to 800kg unbraked/1400kg braked, only thing is there is an outer bracket and the bolts are also clamping that to the rail as well.
As long as it's a high tensile bolt, it shouldn't matter too much for your small trailer?

I'm still keen for a towbar but have done nothing about it to be honest. I'd happily buy an off the sheft Cressida one if I knew it would fit 100%