Hi, I run on a Blacktop banked oval up here in WI. I was running a .28 also. But now have a Go tech 7 port .21 in my late model. I also run a .25 go in my Xray Truggy. The motors run strong. I know the guys in OKC. City (Competion RC) run .21's when the track is loose and .28's when the track has a groove or high bite. "I know most of them that run there"
I hope this helped you out.