Re: cascover queries
My boat Englander was cascover sheethed from new, over iroko, there is not a blemish on it in 40 years, it comes to 6" above the waterline. If it's sound leave it alone. Fasteners can be replaced, by cutting a very small area and then repairing with glass cloth and epoxy, but it will need to be spotless around the area, to make the epoxy stick, keep checking this area, whenever you slip for antifoul. I have never neede3d to replace a fastening, as she is bronze and copper fastened. Most of the horror stories about cascover, are from jobs done later, to "save" an already rotten boat.
If I agreed with you we'd both be wrong.