To protect against further UV exposure, rain, dirt, etc in storage, I constructed a roof cover for my 1978 Trillium
4500. I used UV protection soft Tyvek 1460C. It's light
as a feather, strong enough, not cheap, and at least for me a bear to sew. But it works. Fits like a glove. Doesn't flap around in the wind. More or less waterproof. I like it. As with all of my projects I'm sure there are many out there who could have done a better job, but here it is for your opinion.