Very nice combination.

Attached is a picture of my mount, currently with a PST J600 installed. It was built and originally used with a RAM 500. I wrapped a few layers of wax paper around the Ram 500 and then laid layers of 6 ounce glass half way around until I got the thickness I wanted. I finished with one layer of carbon. The Carbon looks great, but not really needed. The thickness ended up to be 3/32. After it dried, I cut it to final size. It is screwed to the Roo mount surface with four sunk 4-40 screws. If you don't plan on changing it, you could also glue it along with the screws. Don't forget to put about a 1/16" shim between the mount and engine at rear of the engine.

I use a 50 ounce water bottle and a 16 ounce tank next to it. If you really want to use kevlar, I believe Garry Mueller makes a 68 (somewhere around there) ounce tank. I used the 100 when I had a Roo with a Ram 1000, but think that is overkill and just additional weight for the 500.

BTW, the P80/750 mount would be way too big.