I guess I forgot to post the bypass I made, to direct more heat and smoke directly at the smoker/oven. Temps still seem stuck around 300 deg. max. I'm guessing all the "heat sink" of the oven assembly, is just overcoming the output. It also may take some time and fiddling with valves and flow, to get it better.
4" bypass to directly under oven/smoker floor:
and here's my attempt to shrink the top, so it quits bulging when really hot.
I cut 1/8" grooves, and "v" ground them out to 3/16" or so, and then laid about 1/4+" bead, (1/8" 7018 rod @ 110 amps DC+) hoping for enough draw and shrinkage, to put tension on the plate when cold, and allow closer to equilibrium when heated.
pattern, centered on center of bulge, I'm thinking it was asymetrical with the top, due to the smoke shelf position and hot spot where flames transition:
center spiral, for final pull to middle, and fill for grinding flat. (the very center ended up sagging right there):
weld detail, seems penetration was complete, or very nearly so: