Can anyone give me any idea if SUMO rims are good or not? And what the difference between double wall and single wall is?

Dang good question. My observation is that Sumo rims aren't very desireable, but I'm not sure why. You'd be hard pressed to tell one from an Araya at more than three feet. Just the other day I went to build a set of wheels with two Arayas and as I started to lace them I relaized that one was, in fact, a Sumo. I laced it anyhow, and it looks sweet to me.