I would say put some weight up front, especially if you don't have any right now, that will help make your sweet spot a little longer. I would start around 200 - 300, that should be all you need up front. It will knock the height down just a little bit, but it won't effect the ride and its more wave to surf. I would also say go for a little more weight on your surf side.
We just ride with our sacks loose on the seats, never had any real trouble with getting them to stay. We had a 350 fall one day, but it didn't fall again after we put it back. As far as the crew, we just move around the boat. Its just one of those things when it comes to surfing, if you want a good wake, your crew will be have to get used to sacks around the boat.