Attempted to mount the engine today and the frame needs about two more inches of clearance in the down tube around the middle section. planning to make a subtle bend and add some length in the process. Top tube is 1" diameter and the bottom tube is 1.134". I'll make the bend before I cut anywhere and then slug/pin it back together and braze. This modification is out of necessity and will give more room for the tank. It's looking less and less like a 1908 but I hope to keep the old design principals in place.