If I won't be able to get to the back of a joggled joint when weldings finished, I either butt weld instead, or posistion it so that water/moisture cant sit in it, by pointing that edge downwards. If you can get behind it when done, give it a good filling over with a seam sealer.
There were a couple of threads about jogglers a while ago with commebnts from people that have them (need to search joggler and jogglers rather than joggle). Seems the manual type is hard work on anything that isn't very thin.
I was going to get one, mainly for doing body panel repairs, until I read somewhere that when it comes to panel beating the difference in metal thickness caused by the overlap makes things difficult.