The biggest issue is this:
This is where he screwed up the frame:
The two angled pieces that were originally welded onto the spine a few inches higher, blocked the tank from sitting down on the frame all the way.
He could have hammered in the bottom of the tank slightly to make room for these rails and left the frame entirely alone, but NOOOO...
He cut the bends out, moved them down, and welded them back on lower. Then realized that the big bell on the top of the stock CV carb was made to fit right in between those bends! so he hammered in half of the frame tube to make room. You can see the indentation on the left side of the frame. On the right side of the frame, he actually started to hammer the tube in the WRONG WAY!, then stopped, flipped it over, and hammered the rest in; so on the right side, there's an indentation on the TOP of the tube (which you can see in the photo) as well as on the inside of the tube.
Essentially, there's only about a third of this tube left in tact, and these indentations are hammered in exactly where the frame is otherwise unsupported. It's going to collapse right there if it gets any stress at all.
Additionally, even with these indentations, the carb just BARELY fits, and is sure to rattle against the frame if there's even slight vibration from the engine. (I'm guessing a nice big 650 single is gonna vibrate just a tiny bit!)
I bit the bullet, and ordered a VM36 from LANCER, which doesn't have the big diaphragm bell on the top, so it will give me a lot more space to get in there and brace this up. The carb should be here next week sometime, and I'm waiting until it arrives to see how exactly it all fits in before I tackle this at all.
I have a few possible thoughts, and I'm willing to let it be a little ugly since it will all be mostly hidden anyway, but if you have any suggestions I'd love to hear them!
Right now, I am leaning towards using some very solid "U" channel, and bending it to fit inside of these frame rails, then welding that into place along the top and bottom. I may add additional bracing from there... who knows.
I'm half-tempted to get a new frame and start over from scratch!