Evo x rims/tires question

Hi guys, I recently purchased my first Evo, it's a 2011 GSR phantom black with the handling package (bilstein's and bbs rims). I'm getting it lowered in a couple of weeks with swift spec-r springs and I'm considering selling my stock 18x8 bbs/advan's and switching to a 18x9.5 rim with a 265/35-18 tire. The offset I figured might work is between +20 and +25 keeping in mind that the swift spec-r springs will drop me down 1.25" front and 1" rear. My question is does anyone have any experience using the swift spec-r springs with that size of tire? and if so will my offset guess of +20 to +25 work without any fender rubbing?? If not what offset should I be aiming for???

Thanks in advance!
Karl.