I have a mid profile 5th wheel and purchased a cover for it. Searched the internet to find a size where my length would be close to the upper end of the size range to try to get a snug fit.
It seems that the 5th wheel covers are made for full profile trailers so when fitting them to a mid profile, there is a lot of extra fabric. Long story short, a heavy wind pretty much destroyed the cover in about 30 minutes due to all the flapping and billowing.
I got a refund, then purchased an Adco semi custom tyvek cover. Pretty happy with the fit, and it's light enough I can easily haul it up to the roof of my RV , and no, I don't work for Adco - just happy with the product and their service.
PolyPRO 3 sounds good with zipper access panels and 3 years warranty but yes, Goldline is the best choice with 5 years warranty, reinforced corners, wind vents and tyres cover but price is little high.