Thanks Yar.
"1.Trim the pieces to be welded to a perfect fit for butt welding."
So you are aiming for no gap at all between the patch panel and the body? I need to practice some metal shrinking....
Yes, you should trim the panels so they yield a no to very little gap.
Since you are Tig welding, if you take the time and fit the panels right with no gap the best option is to fusion weld. Fusion weld means no filler rod. By using no filler, the warpage is far more constant and easier to correct later.
