Quick question when removing body mount #4 to replace the steel support cup. Once the mount and rubber pieces have been removed is the body section alright to just hang there for a short while or does it need to be propped to stop any damage?

I've seen videos where it looks like it's just hanging there and doesn't seem to be a problem.

i.e here
Also would it be best to do one side at a time rather than have both body mounts out at the same time.

 

Quick answer: Yes (It is okay to hang there)
and Yes (I would do one at a time)...

 

but cutting a hunk of wood to bang in there won't hurt. or even a 18 or so inch of 2x4 between center of rear bumper or spare tire and the ground.

 

Managed one side, what a rubbish job. Sorted it without any major disasters. It was a right nightmare getting all the old rushed and perished bits out, but with a bit of patience I got there. Everything was rotten but the chassis bracket was in really good condition (thank god).

The new support piece was panel bonded in place instead of riveted, it seems the problem with this part is that water is splashed up by the tyres and then sits in the bottom of the cup causing it to rot away, it might be a good idea to apply silicone around the gaps to prevent this on any already installed.

To panel bond the new support I cleaned up the area and ground flush/removed the old rivets then applied the panel bond to the support, then installed and used a trolley jack with a socket bar with a socket that was just small enough to fit through the hole in the chassis mount. I then raised the jack until the socket was firmly pushing the support on to the fibreglass section and let set, worked very well. The whole installation got several coats of a stone chip proof black spray paint so will hopefully be good for another few decades.

The captive nut was shot (the bolt snapped as I tried to unscrew it so was still in the nut) so this was all removed, and I made a large custom washer that fitted in the bottom of the recess on the inside of the mount to spread the load out a but more, this also had a few blobs of panel bond on there to hold it in place. Then used a flange nut on the inside.

The whole thing was then torqued up to 40 ft lbs which is the lower value in the specified range but seemed like more than enough for me.

Anyway here is the new mount and bracket along with another picture of the other side which is still to do which was the better of the two (they were really bad).