Already have a large cover on it when not in use, in addition to Scopeshroud covers round the truss portions, but this doesn’t seem to deter them…
The cover may well encourage the spiders to take up residence I guess, but it’s the lesser of two evils perhaps versus protection against snail poo and any potential water ingress. I’ve used a truss newt before with a tarp over the top when not in use and don’t recall such an issue.
No geckos to deal with in Oxfordshire however!