I have one and the fit is not great. The first one they sent didn't fit at all. I had to take photos/measurements and then send the cover back to the factory (which is in Mexico, not Tennessee as Overtonís rep told me). The second one they shipped fits, but it is not as snug over the bow as I would like it to be. A single pole would not work to hold the cover up in order to keep water from pooling. I ended up making a skeleton of sorts out of PVC that has 3 bows to hold the cover up. It still isn't great, but it gets the job done.
As far as breathability, yeah, it's not great. I use 3 buckets of the stuff that absorbs moisture. Those work really well as I have had no issues of mold/mildew in the six months that Iíve had the cover. The cover does do a great job of keeping the water and dirt out though. I spent about $400 on mine. If I had to do it over I would spend another $200 and get a custom one off cover made from a local canvas shop.