Chriso,
i had exactly the same problem, the glue remains on the original neoprene cover scratched the acrylic dome. Arggghhhh!
I had the same idea to make a hard cover NOT touching the dome and i will do it probably with:
- PVC pipe for sewage with a glued on disk of pvc/wood/aluminium as cover, tube inside covered with neoprene to fit the diameter
- aluminium (difficult to weld but can be attached with rivets)
- plywood (thin plywood to bend the tube and a thicker one for the top, cover with 3/4 layers of resin to make it stronger
- Delrin, expensive material and it need a huge lathe or better a milling machine to machine it
In a few weeks i will be back in Italy and work on that.
Chris