I share your hindsight. My 221 frame also tapers and I am not sure Jacks scuttle will work for me.
Why the lip on the front? I like the angle on the bottom, it looks like the vertical leg is on the inside. I will be putting mine on the outside to bond the skin to.
Although it's hard to see from the photos, the front vertical leg is flush with the outside of the frame with the addition of the lip
, so the scuttle's skin can be bonded to it (as you are doing), and line up exactly with the skin on the side of the body. The front & rear hoops of the scuttle are welded to a piece of 1"X1" angle iron which, in turn, bolts to tabs on the frame. I had to remember to leave about a 1/16" gap between the angle iron and the top edge of the frame, as two layers of aluminum skin will be sandwiched in there (the body's skin + the scuttle's skin).
The lip on the front hoop (1/8"X7/8" flat bar, heated, bent, welded, and massaged into shape) is there so that, when there is a 1/8" layer of foam (ahead of the lip) for the trailing edge of the hood to sit on, the hood's skin will be flush with the skin on top of the scuttle (if that makes sense - it's hard to describe). I wanted the foam in there so the hood won't rattle. There will be, of course, foam on the lip of the nose, as well, so the hood is on foam both front & back. That should also help to protect the paintwork on the nose & scuttle.
MAN, this is complicated!!
I have tried mocking it up with some aluminum flashing bits, and it looks like it's going to work...