I run 33's on my IFS. I believe there are some others here that have 35's on their IFS. Maybe they will give you some information. Try doing a search and see if it has been discussed before. 
Thanks Gonzo,
I have heard that the"max" size for IFS is 35s, Or at least thats what some people say. I dont think I will ever go any larger than that. Of course, I said that about the 33s
