I actually did this on a 93 Navigator I previously owned. That RV had a farily substantial roof assembly. I fabricated the frame to fit in between the cross members and drilled and bolted it in several places. I spring loaded the assembly to make it easier to raise or lower. I did not install a motor to operate it electrically. When I had it all installed I made an oak frame around it to match the cabinets in the RV. Had a lot of people comment on it and it worked great. Had a 40 inch tv mounted in it. Of course if I had it to do over, I would probably purchase something electric already made. In my case the RV had already suffered a refrigerator fire so I was replacing the ceiling anyway.