Hi 2000GT,
IMO, if the job is done and they did a reasonably good job I would leave
it and do my best to seal up the backside lap. That is the negative on a lap
joint, moisture attacking from the rear! Structurally, a lap joint like you've
got there is actually stronger than a butt joint. How to seal it up? Well, body
solder would probably be the best but hard to do in tight spots and cleaning
or neutralizing the flux is very very important. Otherwise that could actually
get the rusting process cranked up that much faster. I suppose a couple coats
of epoxy primer on the backside followed by a auto body seam sealer manually
worked into the seam would offer good protection along with making sure any
moisture back there finds its way out thru open drains. Getting everything lined
up properly is the hardest battle, so if that is already done for you to your
satisfaction, then cutting it back out because they used a lap joint would be
hard for me to do! My
and goodluck with what you decide to do! Jeff