Suggestions on strengthening jack attach point.

The camper manufacturers should have a bracketed truss at the corner on the inside and have the jack on the side pushing up, much as the way floor joists are supported with a pier and perimeter foundation. This would cradle the load and distribute the force away from the base area where the jack is located.

Obviously the manufacturers build their products to last 10 years or less and when I was looking for a used Lance there were very few that were even that old that were available.