I think it might be safe for me to state, "a camper's corners, and the ends of the wings, may well suffer more abuse than anywhere else on a camper."
The corners are where the jacks mount and the jacks have likely been levered back and forth and sideways many multiple times over the camper's life for several reasons, but perhaps mostly from loading and unloading as the truck isn't exactly straight to the camper and an owner uses muscle to push the camper one way or another. Or the camper isn't high enough and scrapes a little on the bed of the truck. Or maybe a jack end took a hit on a boulder or dragged a bush once.
The wing ends are normally where the tie-downs are located. No owner wants to lose their camper so they make sure it's tight, right? Sometimes too tight. Maybe before they pull out of the driveway they've already started to pull some of the wing fasteners out of the rest of the structure! Then the bed flexes over uneven terrain and the flex forces more destruction.
These places are typically quite tender, and more often than not manufacturers haven't designed them well enough to withstand normal use, let alone abuse.
For an old stick frame camper, water can easily get into these corner areas from jack bracket installations that either weren't designed well or were aftermarket slop-ons by a well-meaning home owner or a novice RV service tech who is thinking more about his high-school girlfriend at the moment when he starts screwing lag bolts into your several thousand dollar investment.
I mentioned early, "Don't put corner jacks on a travel queen". Here's why. While the front and back walls are 5/8" plywood, the side wall framing in the corner are pieces of 1x2. Vertical pieces differing in length by the interruption of horizontal 1 bys. When you screw lag bolts into the camper sidewall, your first surface is metal skin, then 1/4" fiberglass batt, then pieces of 1x2, and finally 1/8" birch paneling (the interior wall surface). Yeah I know, the brackets are designed to put the lags into the plywood ends, etc. I still say it's just a way to begin wood breakdown.
Someone bypassed Lil' Queeny's manufacturer designed Saf-T-Jack mount system (an under-wing metal grid fastened to both the front and back walls and the wing) and installed standard hydraulic corner jacks. Lil' Queeny's wood under the metal and fiberglass is looking really good over-all (from what I can see so far) but the corners are destroyed, both by the jack bracket lag bolts, and the resulting water damage from opening the corners up to water intrusion. Doesn't matter how much silicon you slop on stuff, if your fastener doesn't gain purchase, the joint will leak and the water will get in. Or if you bang the jack, it will weaken the fastener's grip (lag bolt into plywood edge?) and moisture will get in.
We'll get more detailed as the project goes on but for now, here are some pictures of parts of the under-wing grid, along with - in two photos (from the larger donor camper) - the horizontal tubes of the jacks extending into the grid frame, and in the other photos (Lil' Queeny) - previous owner designed tie-down eye bolts in pipe pieces.
This owner designed tie down is probably not the best design either. For one thing, the rear tie downs are much too far forward (the pipe holes are positioned based on each camper's center of gravity). Secondly they are all too far inboard. Even if you got longer pipes and put the eye-bolt far enough outboard for properly locating the tie-down mount, you are extending leverage onto the metal grid, setting yourself up for wing structural failure.
I am not an engineer; nor am I a camper designer and I haven't even played one of those on TV, and I don't really much stay at Holiday Inn Expresses, but I firmly believe this....
A camper corner structure (front/back wall, side wall, and under-wing surface), must be tied together well or there will be problems. If the camper is large and heavy enough, it may well be the manufacturer has tied these together well (or not). If the camper is light-weight, or thin-walled, I wouldn't trust them (the corner or the manufacturer). Lags will loosen; use bolts and nuts. Use some sort of metal gussets inside and out. Sandwich the camper between them. That's why interior access is a must. For me.
I have to replace the wood of the: wings, at least the back wall, perhaps the front wall (inside the bed), and the lower side walls. I will fabricate such metal gussets when I assemble. These gussets will incorporate properly positioned tie-down locations and provide a proper mounting for a future corner jack should I (or a subsequent owner) decide to install corner jacks.
My plan is to use the donor camper's Saf-T-Jack system, cut to proper size and rebuilt as needed to use on Lil' Queeny. Alternatively I have two portable side jacks that work very effectively for loading and unloading, which I will use in conjunction with the metal grid and a slight modification. I like the idea of leaving the rock grabbing and extra weight of camper jacks home when I get on the road.
