RE: engine for Extra 230
An AX120 should do the job nicely. I had one in a 72" ESM FW190 (the old all composite one) and it hauled the 17 odd lbs around pretty good!
Mind you, if it was me I'd go for a 30cc gasser too. Got a 73" Giles 202 in a box and an MLD 35 in another, gonna bring them together one day!
Terry