Well I bought an 1800 bimini.
It was a couple inches wider where it mounts, but it easily attached to the stock side mounted attach points. Although it fits, I think I am going to buy a smaller one. I like the look of the small factory top. The 1800 top is not only wider, but longer so it your looking for a lot of sun coverage, it may be the way to go for you if you have a 15' sea-doo. With the 1800 top down the stock cover has a hard time getting over it on one of the corners.
Hopefully this will help someone else out one day that tries to do the same thing.