I raced mod and 17.5 on a parking lot track. The two are night and day. The weight transfer is tremendous in mod and I use a 5.5 with no boost running a 7.0 FDR. 7.5 with boost would be no different. The most noticeable difference between mod and 17.5 is tire wear. A new set of tires running 17.5 can last you for months, while that same set in mod will only last you 2-3 race days.