[sal98]

You could get away with it as long as you have at least 1150-1200 square inches of wing area on the plane. A good 50cc engine like the Da, DL or Evolution will weigh in at around 3pounds. I have even seen 50cc engines on Profile type aircraft. Just beef up the firewall a little and use good throttle management. Guys are know adding 50cc powerplants on 25% planes with great success.