Slight waviness is normal. The fiberglass is pretty thin. Normally it is not too noticeable, but if the light
comes from an oblique angle it can be accentuated. If all the interior cabinets and supports are in place, and if all the rivets are tight (give the acorn nuts on the inside a twist with your fingers), then I wouldn’t worry.
Do check the frame underneath carefully, especially under the front of the cabin where the A-frame bends. Scamp
used a lighter frame on these older units and occasional failures do occur, most commonly on the street side bend.