Mine had originally been setup for water tanks. It was converted
years ago to have water bags. It is an earlier model Cirrus.

The old bags do look like they held about 10 gallons each. That's
around 160 lbs total water weight. Not alot, but when you consider
some adult weigh 160 lbs, that then seems to be like alot of weight.
I can tell the difference flying a two seat either solo or with
another 160 lb adult in it.

If anyone has an old bag of some sort that might be converted.... send
me an email to scott.alexander (at) jetblue dot com