I'm not an offset expert, but as long as you get the right offset, you could run 295/30R19 tires on the rear without trimming with a 10" or 10.5" rim. I didn't recommend a 10.5" rear to you in the previous post because I personally think a 275 would look absolutely retarded on it (I HATE the stretched look).
Probably the best setup for a street ISF is 19x9 fronts and 19x10.5 rears, running 255/35R19 and 295/30R19 tires. I'm just personally sick of seeing so many ISFs out there running heavy 20x11 rears and only putting a 285mm tire on it.
2008 Lexus IS F - SGM - JoeZ intake pipe, Tom's filter, Borla catback exhaust, 30% tint all around, 245/35R19 and 275/30R19 Continental DWS tires
2006 Honda CBR1000RR - Akrapovic Evolution Line Race Exhaust, BMC Race Air Filters, Vortec Rear Sets, Bazzaz Tuner, Dyno Mapped
2000 Honda S2000 (Sold and missed)- AP2 in an AP1, BC coilovers, Prodrive monoblock forged wheels, etc.
"ENTHUSIASM IS NOT A SUBSTITUTE FOR CAPABILITY" "Be ashamed to die until you have done something good for mankind."