I never thought of the possible resonance problem. I have resorted to putting construction grade 2 X 4 behind the engine mount on my built up fuselage type planes to get the engine far enough forward. Not pretty, but has worked. I worry that the longer moment arm of the engine being so far forward might twist off the firewall. Thanks for your response. Now I know I'm not plane crazy. I will take this into consideration before I buy any new planes.