Dude, if you only put that 750# sac in the rear of on Outback, you are going to be dissapointed. The wake will be crappy, the boat will struggle to get on plane, and it won't drive worth a damn. Trust me, we used to do the same thing with my Outback. We had so much weight in the back, the platform was under water 6-8 inches, and the wake was crap. The general rule of thumb for weighting a boat is 60% rear & 40% front. Well, with an Outback, I have had the best results doing the opposite. Also, when my boat is loaded and has the best wake, the platform is barely any deeper in the water than when the sacs are all empty.