I fly a Bandito Grande at 82"ws and 14lbs using a ryobi 31cc. Perfect match, flys like a lively sport plane. Plenty of excess power for screamin fly bys and quick climbouts. I did some major mods to make the ryobi work but nothing that couldnt be handled by any builder. Just had to move the firewall back 3 1/4" to get it to balance without any led. Just speculating, but 40cc and higher might be too much for that arf airframe. They generally arent glued as good as stick built plane from my past experience.
Edwin