ORIGINAL: MTK
......I have ideas in mind for new, larger, all wood airframe with retracts for it.......
Years ago, pre-electric pattern, something like this was done called the Petrol Petrel. F3A legal with a ZDZ 40. If I remember right, vibration was a problem. I only saw it fly a few times. You may have a good handle on that. The ZDZ can't match the power of today's Chinese engines, even of smaller displacement, so a modern 40 something may work OK.
The lack of vibration is the biggest attraction of electric for me.