i tacked welded CP16 into place then welded approx 2 inches on the engine bay side swapping from side to side then top until fully seam welded, tho i used 3mm steel plate so my plate could take a bit more heat than the suggested plate thickness,
just take it slow & allow each stitch weld to fully cool before doing the next one.
As for the diff brackets, again i tack welded (3 tacks = both ends & the middle)
then put the bracket into a vice & clamped the other flat to the vice & fully seam weld, thankfully they stayed "True square".
hope that helps.
andy