Still, if it was my @ss on the line with this project, seriously, I would definately go back in there and fill those suckers up, both the t-joint and the plate to tank seam, and crank it up too!
Please, don't think I'm trying to ridicule you. Only trying to help.
On your shop work, your Millermatic 251 is capable of spray transfer with .035 wire. Pick up a bottle of 98/2 argon/oxygen so you can play with spray. If you have future heavy plate jobs and want to use solid wire and gas, spray it. The welds will go in alot hotter, wetter, deeper penetrating and better fusing, cleaner too. Must be used flat/horizontal only, no out of position. Anything over 1/4" should be sprayed rather than short circuited, with mig solid wire. Play around with it, you'll love it!