I just finished mine tonight and I used 540# LAUNCH Sacks. They have four holes with one on the side for drain pump, two on top for fill and vent/overfill. Took me about 2 hours.
Phil, I bought 12 ft. of 1" OD hose and 4-3/4" two sided barbs and 4-1 1/2" hose clamps. Taking out the tanks was a pain, but adding the bags and hose was a cinch. I plan to take pics tommorrow and will post for you. No hose needs to be replaced, just lengthened for fill and and vent. The empty pump fits perfect to the LAUNCH sack.
Here's a picture, but go to MalibuBoatOwners.com for a complete set of pictures in my gallery and a description of how to do the project and what you need. LAUNCH PADS come from OVERTONS or BARTS, but I got mine from dealer.