Some great advice in here.
I installed my AEV corners about 6 years ago and just recently took them off to put the EVO Builder Corners in-place. Of course rust isn't really an issue here in AZ, but I was happy to see the body panel underneath was preserved just the way it was when they were covered up.
One more pointer here, in case you do happen to mess-up on a nutsert, the method I used to remove my old ones was to take a grinder to the outside edge and grind it down, gentle not to get any paint. Then when there was very little left, bang the nutsert into the body and retrieve if you can. (The AEV ones had to be removed since the edge sticks out about twice as much as the ones EVO supplied.)
I can't stress enough to put your skins on bare metal for their initial fitment. You want to get them in exactly the right position before you go drilling holes. Ratchet straps, c-clamps, hammering... Are all useful techniques to get it in the right spot and much easier when you don't have to worry about damaging a painted or powder coated finish.
Ran them bare steel for a weekend after instal. (Note: I damaged the rear upper plate on a rock wall. So I just removed it)
Pic of the panel that will be hidden when the EVO corners come back from Powdercoat
Our buddy simulating a spare tire on UTIADAM's new carrier..