[slicer]

The most common offset I see used for 10" wide wheels in the front is et25 (offset that Apex uses on their 18 x 10 wheel). The only negative is that you need an et20 to clear KW clubsport coilovers. Since you have the sleeve-over kit you should be ok with et25 (I don't think the SO kit creates inner clearance issues - but I have never had them). Be prepared to add some negative camber with et25 and even more with et20.

On the rear I have had et29 and et30 in 11" rims. That offset works well. I think you could technically go with something lower (volk re30's are sold in 18 x 11 et18 offset) but the 305's are going to limit you. No matter what you are going to be close on both the inside of the liner and the outside of the fender with an 11" wide wheel and 305's. It's going to come down to mm's. I don't think I would try an offset any higher than et30 because I have minimal clearance on the inner fender liner with 18 x 11 et30 wheels and Michelin PSS in 285/35/18 size. I had 20 x 11 et29 wheels, 305/25/20 pirelli p-zero's with eibach springs a few years back. No rubbing with that set-up but the RE11's run wider.