There may be 2 support structures, 14" apart, running the length of you coach. That's what Fleetwood did when they built my 95 Bounder. Get a stud finder and have a look. You could fasten to those supports if they exist.
95 Bounder 32H F53 460 2013 CRV Toad 2 Segways in Toad First brake job 1941 Hudson