Most extreme wheel/tire fitment for ATS AWD

Hey guys, new this forum and have been searching for a thread that already discusses this without any luck. I have an ATS 3.6L AWD Premium that is being shipped and will arrive in two weeks. Once I have it I can do the necessary wheel removal and investigation into seeing what will fit- until then I was hoping someone might have already figured out what the largest wheel/tire size is possible for the AWD. I want to do the same size for front and rear... then I can rotate. Plus I personally think it looks better when all the wheels are concave, not when the rear is and the front is a flat spoke pattern.

I am willing to do some cutting/grinding/fender rolling if needed to go big.

I am wanting to do a 20x10 with a 275/30-20. Initial calculations look like I could accomplish this with a +30-35 MM offset but that's only taking into account the outward (fender) side of the car. What I don't know is if there would be interference with the struts or spring perch. With a +33 MM offset this size would extend outward 1.26" and inward .71" more than the stock 225/40-18.

I'm fairly certain the rear won't be an issue... it's the front that is the big unknown to me.

If I can't go with this I will do 20x9 with 255/30-20 and a 25-30 MM offset.

If there has already been a discussion about this particular set up please point me in that direction.

Thanks in advance for any help!

GH