RV covers are made of varying fabrics, some of which are different types of Tyvek from my understanding. They are used to provide UV, rain, and weather protection overall.

You can still utlize the heavier fabric to make the gear you want. If it works for you then spend the money for the lighterweight Tyvek. Some folks don't care for Tyvek after all the trouble of aquiring and making the gear <img src="/forums/images/graemlins/smirk.gif" alt="" />