Just looking at pictures of the Winnie Minnie models on Winnebago's website, I noticed these two issues with it's roof - regardless of it being a one-piece fiberglass one:
1. Looking at pictures showing the back and the front of the motorhome, the roof appears to be nearly, or fully, flat - instead of crowned. In addition to being stronger, a crowned roof helps water to continuously run off well around vent and air conditioner openings in the rain or when being washed.
2. Looking at pictures showing the sides of the motorhome, the edges of the fiberglass roof do not appear to be rolled over the top edges of the side walls very much, if at all. This method of keeping water from leaking along the roof-sidewalls interface is just about the "perfect" one. The more inches the roof rolls down over the top of the sidewalls - the better.
2005 E450 Itasca 24V Class C