I gritblasted the inside of the tank and noticed a few small dents here and there on the tank. Aad welded a large ballbearing to a piece of roundbar and taped a little laserpointer above the ballbearing so that the red dot from the laser was on the center of the ball.
By positioning the tank over this tool so the red dot was in a dent it was fairly simple to tap out the dent. When all the dents were removed Aad welded in the new patch panel. The new piece will need a little bit of shrinking and then it will be perfect!