The first thing i would do if i were new to foams is get some practice. I alway run either plaid or double purple in front and always purple in rear. Compared to rubber tires foams require more finess and it really pays to be smooth, thus practice. And if you chunk a tire don't worry about it. If your competing for the national champs you would put new ones on. But the amount of differece it makes is little. Depending on your track, one side of the car might wear more than the other so check them with a caliper and rotate them. The bottom line is smooth is the way to go due to the increased traction and once you get smooth dial the rest of the car in to get corner speed!