Aluminum Roof Repair on '78 Pace Arrow

I'm with you on removing the roof to fix what is underneath. Any sag you see is some sort of structural problem that needs to be fixed. Most likely something rotted away. Older coaches like that had a lot of wood in the roof. We had both a "Leisure Lodge" and an old Winnebago from that time frame and both required a lot of roof rebuilding. The good news is that you are not really talking about a lot of materials and a cheap blue tarp from Harbor Freight will let you work on it at your leisure. The minimal material cost will be far outweighed by the time you spend doing it. Just take your time, don't get in a hurry and do it right the first time. Fix it right and you won't have to deal with it again. You'll find lots of help here. Post what you find (you are not going to really know what's up until you get the roof opened up) and you'll get lots of help!