When I replaced my unit with a compressor refer, I put four lag bolts through the base framework of the refer anchoring it to the floor. All trim work was attached to the surounding woodwork and not the refer. The refer has not moved. Trim work WILL NOT SECURE THE REFER. Yes, it was tricky reaching under the refer with the bottom panel off to fully secure the unit but it worked.
If you cannot get access to secure all four corners of the frame to the floor, do as the above post (smlranger) describes. If you don't do one or both, you will someday find the refer flying into the middle of the coach.