Has anybody done 18's in the rear and 17's in the front, and how wide can I go in the front?

 

You can use 18" on the rear and 17" on the front. You can use the following tires in front on 17x8 or 8.5 225/45ZR17 and 235/40ZR17 and on the rear 18x9.5 or 10
265/35ZR18. I had these on my FD. If you lower your FD I dont think you can put wider tires. Also check your offsets.