Yes the single modules are 483mm x 483mm and the doubles are 483mm x 966mm.
We try to use doubles wherever possible as this increases the strength of the overall structure and helps to reduce the cost too.
Our 'drive-on' module is 483mm x 966mm.
Regarding pricing, I can quote for complete docks or pontoons but don't really want to post an item by item price list here.
However, I note your rib is a Cougar R8 which I believe has a stepped hull. Unfortunately, stepped hulls are a problem for us when we try to drive off the Aqua-dock as the steps tend to sit firmly behind the rollers. We have to be honest here and say that although we believe our product is brilliant for standard hulls it won't work with a stepped hull. In fact our knowledge is that drive-on docks don't work generally with stepped hulls and the inclusion of our rollers certainly don't improve this.
Happy to quote for anything else though.