Tire width and rim question

Im about to get new rims and tires for my GTX. I'm looking on getting a set ot torque thrust M wheels(black ones)in 18x9 on the rear. For tires, i was looking at the nitto drag radial NT05R in 305/45 18. On the Nitto site, it says the recomended rim size is 9.5-11.5. I would get a 18x10 wheel, but the backspacing offered is to much in the 10 inch rim. Even with the 9 inch rim, I might have to run a little spacer anyways. My question is, does anybody think a half inch smaller than recomended is gonna be a problem?? I would not think so, just looking for some thoughts from others,thanks

It seems okay here. I've seen 9 inch slicks mounted on 15x7 rims at the dragstrip many times. As long as the tires have 3/4" of clearance to the springs and body, make the move!