Noticed the floor is spongy on our 2009 Flafstaff TT It's been setup for 2 years on a site in Delware. At first I thought it was the stabilizer jacks being used this long but now I'am thinking it's...
What I did with mine was overlay the heavy traffic areas like the kitchen and bathroom areas with half inch particle board. I removed it when I traded it in. The lightweight materials that Flagstaff and their sister Rockwood used to lose weight was not always the sturdiest.