Depending on the construction of the rig, you can do many things. If the ceiling panels are 4X8 sheets of lauan plywood they are most likely stapled to the ceiling joists. I had a fifth wheel that was constructed this way, with an aluminum frame. The ceiling panels started to sag because the staples were pulling out of the aluminum frame, where they actually made it into the frame. I fixed it by removing the staples and replacing them with tiny screws - I drilled through the panel and the aluminum and installed the screws. Then I replaced the slats that were used to hide the seams with new ones, using double-sided carpet tape to attach them to the ceiling.
In your case, if the frame is wood you can still do a similar repair - just select some small wood screws to replace the staples, then hide the screw heads with some strips of material of your choice.
Alan Hepburn - San Jose, Ca
2007 Bounder 35E being pushed by a 2008 smart fortwo Passion
Good Sam Member #566004 * FMCA Member #F431612