Advice on a sleeve for inside the longitudinal Options

[doug_b_928]

I'm repairing the passenger long. I've removed the rust and welded in two patches that comprise the bottom 2/3 of the long. To strengthen the long due to the welding I've made a sleeve out of 18 gauge cold rolled (same material as the patches) that is 36" long as pictured below.



The problem is that the 90 degree bend in the sleeve has made it tough to bend to the exact shape of the long for a tight fit. I put clamps on it and then with a hammer and punch beat it at the back (as shown by all of the pock marks). I think if I start welding it at the front and then do the hammer and punch thing as I go along it will probably conform to the long. But, I'm not 100% sure and would hate to have it half welded in and realize that the last 1/3 will not fit tightly. I could also make an 18" relief cut along the bend, bend it to conform, and then weld the sleeve to that shape prior to welding it to the long.

I was going to run a bead on the black lines to make it more stiff, but figured that would make it even harder to make conform to the shape of the long when welding it in. So, I guess another advantage to the relief cut method might be that I could put a couple of beads in the sleeve (though perhaps that might also throw the fitment out of whack and put me back to square one with welding it in being more difficult).

So, my question is, which is the best way to proceed. Take a chance on being able to bend it as I weld, or make the relief cut to fit it prior to welding it in? And, if the latter, should I put a couple of beads on the sleeve?