Decided to keep working on it tonight.
So to make the inner handle, I took a piece of tube the same size as the outside and cut a half inch sliver out of it lengthwise.
Working at it with a vice and snipe bar, I gradually worked it inwards while keeping it round-ish. This meant working the tube inwards at various rotations.
I wound up having to slice about two more 1/4" wide slivers out; the trick is to do it gradually so you don't wind up to small. Eventually, I wound up with this.
I tacked up the seam, welded one end about an inch and ground that flush. I cut a collar and welded it on one end.
Then ground the weld flush and cleaned up the inside edge with the die grinder.
To keep it from warping, I did one set of stitch welds, followed by the second set.
I then ground the weld flush.
Stubby?
Then I cut the outer handle.
The handle came out fairly straight so we're good in that department; I need to do a bit of work on the inner handle and collar ends to get a consistent gap and free up a few points that hang up the rotation, but I'm pretty happy with it so far. Admittedly, the collar is by no means screen accurate; I honestly have no idea what keeps the outer handle from falling off; I'll probably wind up sanding it down to a lower profile at some point.