To actually answer in a simple fashion that is probably wrong but gives you an answer that you can actually use:
Cats, for the most part, follow the same rules as other displacment hull boats. The very simplified way to calculate maximum speed is:
Maximum speed(in knots) = square root (waterline length(in feet)) times a constant
The constant is related to the ratio of the waterline length and the waterline width. For big heavy boats the constant is fairly easy to calculate, it's 1.2-1.5. For little boats it's not so easy. Little boats move a lot with respect to the water and lift from the hulls and sails come into play. My guess is the constant for TheMightyHobie18 is ~5.5. Which means at 25 kts, your boat is trying to plane.
I would be careful at speeds above 22 kts. On many cats, the stern trys to plane first and the bow digs in. With all the weight you have on the stern, I don't really know what will happen.
