I had a WW 3905 and for the first 1 1/2 years I owned it it spennt more time at WW factory trying to get the wall sag problem fixed than I had it at my house. be careful because they cause a lot of damage fixing it each of the 4 times it went back . Eachtime they worked on it when i got it back something else was wrong. One of the main things that happened to it is that when they jacked the walls up the sidewall at the corner where the slide is cracked.They way the solveed the sag problem was they doubled the out riggers.