Must be the Airemax? Well personally at 7 Lbs a YS 91FZ would be gr8 4 stroke in there. 2 Stroke back on my Phoenix 8 I had an HB 61 Piped in the 88 Nationals Even made the Magazine that year with it gr8 reliable motor.

Basically Pete any Quality 61 Piped would work just fine at that weight as well any of the 91 4strokes will do fine. I'm going to throw up now but the Saito 100 being 550 g's would be nice as well.

Bottom line it's going to be your final decision that your going to please and no one else.