I have the 750s in the rear lockers without any issues. For up front, I saved money and bought the V-Drive set (pair) at 400# each, I just fill them as much as the space allows. The V-Drive bags won't work with a piggyback system if using them up front as you can't fill them all the way, but if using a Tsunami, it works great. A 55# Fat Sac brick works well for adjusting for people in the boat if more heavily weighted on on side or the other.
Never Mind The Bollocks, Here's The X-Star