Mattjj I sent you an email. I'm interested in the custom sac, but I'd like to know the dimensions of it and possibly see some pics of how it fits in there. I tried installing the ProX 750lb bag, but as soon as you go from plane to stop the water in the sac rushed forward, making the bag roll forward. Didn't look too good! I was hoping for a sac that stayed under the seat and out of the way.