Agree with the other posters... spend the money.. .because you want to be sure your tires are set up right especially if you're hitting 120-180 mph. I know I feel better knowing the shop has done it.
I get a better price as well for dropping off my rims and having the shop do them. Usually about $15 per tire. $30 for that kind of peace of mind is cheap.
Glad you got it done for free though... free is always "more gooder"
As long as he knows what he's doing and can balance properly.