That's the thing though, I used that, and according to it the front 17x8 235/45 +35 would be 0mm flush with the fender, so it sounds like it would work...(likewise for 17x9 255/40 +38 would have 3mm clearance with the fenders according to the calculator, but lumix just mentioned having troubles with 235/40/17 17 x 9 +35) yet, all the research I have done seems to indicate that anything bigger than 215/40/17 +35 (front) would most likely cause issues, which is probably why I am quite confused as to how to know for sure.

I put your sizes in the calculator and the rolling diameter is much larger then standard. This is what causes the problems.
215/40/17 at the front is the best option and have the best chance of fitting. Guards would prob need to be rolled if your lowered on a 17x8 +35
and a 255/40/17 or 245/40/17 at the rear would work but you'd very likely need to roll the guards if your lowered on the 17x9 +38.
 
In my opinion the wheel sizes are great. Front and rear flush. You just need to right tyres and possible pre-work (rolling)
 
Spend a few hours reading through the wheel threads on MR2OC. Pretty much every combination you can think of has been tried.

I agree with Mrskylighter, good advice. The rolling diameter is what is going to cause the problems at the front. 
 
I'm running stock suspension and 215/40/17 (Front) is fine, keeps the rolling diameter close to factory. I should also mention I'm running Federal 595-SS tyres and I would say they are slightly wider due to the lip protection they have, compared to a tyre that doesn't. I have uploaded a couple of pictures to show what I mean about the lip protection and where it is scrubs on my rear with the 235/40/17 due to the guards not being rolled up.
 
Front. Showing the 595-SS lip protection. It makes the side wall of the tyre stick out from the guard, there is also a lip on the inside of the tyre that makes it sit extremely close to my strut. So when looking for new tyres take into account the overall design. 

 
Photo of the rear looking up. You can see the where the tyre 235/40/17 on 17 x 9 +35 just scrubs the guard. With 255/40/17 I would say you will need to roll up the lip to fit the wider tyre.

 

Cheers, I think it makes more sense to me. I was only looking at the width to make sure it doesn't hit the suspension on the inside, and the fender on the outside, but the bigger rolling diameter means the tyres fill more of the wheel well (since they are taller) and increase the chances of the guard/ fender hitting the tyres when the suspension travels down, right?
On mr2oc someone had 255/40/17 +38 on a 17x9 and he said he didn't had any problems (so did Dylan, but not sure what offset he had), but his suspension/ alignment may have been the reason for this, so it might not work for me.

dylmrt
For reference I've run 215/40/17 up front and 255/40 on the rear with a 17" without problems.
 
with the 265/35/18 i've got now, there will be the occasional scrub on heavy drops.
 
 

Hi dylmrt
 
I was just curious what rim size offsets you are running with your tires? as I would also like to fit a 265/35/18 on mine as well.

The 255/40 rear tyres will be fine if your willing to make adjustments to other things to ensure they fit well (either camber, guard rolling or both)
If you want to bolt them on and not touch anything else then you'd probably want a narrower tyre 235/40. This would likely match the front tyre stretch.