Wheel fitments... 15X wide

[4000GT]

I currently have 15X8 -10 all round, and I am running some R888 DOT slicks. And I want to look to running 250/585R15 (front) and 275/585R15 (rear) Dunlop Slicks. The front and rears sit reasonably flush (front with around -3 degrees of camber and +3.5 of castor.

By my calculations I can run 15X9.5 for the 275/585R15, and the wheel I am looking at comes in 15X9.5 +3. That means 32mm less clearance on the inner guard, and 6mm extra spacing out on the guard, which I think will be ok.

The fronts are a little more tricky, I will need a 15X9 for the 250/585R15, but am unsure what offset might work to ensure acceptable clearance, anyone had experience with this? I want to avoid running flares if I can...