Listern Swaggers all you really need is a silver sided tarp or similar off the roof of the camper . Tropical fly is the term to stop the full sun then the air space between it & the roof of the CT will be at ambient tair temp . All you need to do is block the direct suns rays on the roof . I have done just that with a raised roof spacer on the top ridge & 4 long poles to stretch the tarp out .
Keeps the sap & crap off the roof , bolcking the sun . Wholr lot @ $ 180 at any camping store . My tent maker quoted v$999 for tropical fly, DREAMING .I now use a 3.5x7m plastic tarp from Annaconda Have a think outside the square .