They do other sacs also but the custom sac he made for me is awesome. He did a 9x28x80 sac for under my floor. Very reasonably priced also. I had him put on 3 of the 1" nozzles. The other very nice thing is that the nozzles are made of abs or pvc so you plumb right onto them instead of the flimsy nozzles on sacs like my old fly high. The material is a very tough, zodiac type of material. Too cool.
I actually use the sac upside down. The nozzles you see are on the bottom. One is capped and the other hole on the other side and top of the fill hole I use for the vent line. He will put them anywhere you want them though. I went with this in case I ever want to change my ballast system and I can also use my atwood 750 on the top capped line if my pump ever fails. I did use flow rite quick release in case I ever want to pull the sac out.
Be careful you don't overfill since you're putting that in the ski locker area. I did a search on this site over the weekend, and I ran across a thread where some guy's vent got plugged, and the pumps pumped so much water in the ballast that it damaged the boat. I would hate to see you damage your boat. I know it got me to reconsider my original ideas for concealed ballast.