I will third the motion on Magnum .15's. Heck, I am running one on my Open-A plane even, just because I can almost buy 3 of them for what one OS CV-A costs, and it runs soooo good.

Only problem I have had with Magnums is the carb, ya gotta keep track of all the screws. I have had them loosen up on me and bind up the carb barrel, etc... on my .28's