That "seam" above the belly band is not something I have seen before. Scamp hand lays a strip of fiberglass mat around the inside of the belly band to seal and bond the two halves together. It looks like that might be about where it ends. I wouldn't be too concerned, but you could monitor it for any change over time.
The window dimple reflects a general weakness/flex in that area. My newer Scamp looks about the same, perhaps not so pronounced. The Scamp shell depends on much of the interior cabinetry for its strength. The closet by the door and the vertical support between the galley and upper cabinet support the upper shell. If you wanted to provide additional support near the kitchen window, it wouldn't be too hard to add another twisty metal support on the stove end of the galley matching the one on the sink end. Scamp sells them, or you could make your own support of some kind. A little gentle pressure to the roof in that area before adding the support might take out some of the dimple. I'm not saying it's necessary, but it couldn't hurt.
I agree with Gordon- Scamp's fiberglass work is not high precision or top quality, and it's pretty thin, so some waviness is par for the course and not a cause for concern. This shell has survived 34 years and, barring mishap, it should be around a few more.
Fiberglass failures not related to a traumatic event (like a tire blowout) more typically involve stress cracks around windows
and doors. Once in a while the belly band develops a leak due to a failure of the inner sealing strip, not often. I've also seen one or two with severe UV weathering in which the outer gelcoat was completely gone in spots and it was eating into the fibers. Time to fill, sand, and paint
The frame and shell attachment also deserve a close inspection. Some shell issues can be traced to a loss of frame support around the perimeter of the shell. Make sure the frame is not cracked or deeply rusted. In addition, make sure the shell is solidly fiberglassed to the floor all around. Finally, make sure your axle
has some life left in it. An aged-out axle
makes for a very harsh ride, which is not great for frame, shell, or anything else.