Originally Posted by maniac57
That's a lot of engine to hang off that single downtube...I'd be worried about fatigue cracking at the steering tube and/or the bottom bracket. Even with thicker than normal tubing, I'd seriously consider bracing it better with some triangulation or heavy gusseting. It looks to me like it will act as a sort of spring and you're putting a lot of faith in one tube.
Just my opinion from 30 years of welding and fabrication.
You should be able to figure something to keep the look you like without compromising strength. Maybe a flat strip welded the length of the tube to add vertical load strength?
You have the skills, think about it.
I can see your points and here is a virtual mock up...
I was already planning on beefing up the area where the engine will mount. I do thank you for your concerns on this.