You need more weight for a good wave with the x45. We usually run with a 750 in the rear locker and several bags on the seats, including one more 750 on the seat as well as a few smaller 375lb bags, one on the seat in front of the 750, one in the bow seat and another on the floor keeping the 750 propped up on the seat. I also have a smaller "fat buddy" that has handles and can be moved around to dial the wave.
Once you get the wave really dialed in you will understand, with the right amount of ballast the x45 produces an amazing surf wake. Here is a video of our wave, you can see the 750 on the seat:
http://www.youtube.com/x45surfer#play/all/uploads-all/2/MIL_2pONqHM it gets a lot bigger and better I think we were in some rough open water that day and were running with less ballast. Notice my crazy friend hiking out the side to improve my wave. While I don't endorse this it definitely got us thinking about weights that could hang on the tower.