ric wrote:
I prefer the extra small size top, no matter what size vessels they're covering.
I saw a lady driving a convertible once with vanity plates that said 'toplss'. Even better than extra small size tops

My suggestion is to measure to the outside of your gunnel. I would not mount to your window frame if you can avoid it. Basically look and see where you can mount easy enough, not modify your cover and get behind the mount location for backer boards. I would look at sunbrella fabric, upgrading to stainless hardware, and getting the rear support poles. That will help stabilize/minimize the bimini from side-side vibration. You're probably going to want something like a 3-bow 6' bimini. Do a quick search on the boards here and you'll find some topics on bimini's to get some ideas.