It doesn't appear to use much juice, I'm still on the 12l we first put in it, and have been out twice now for a couple of hours. It's probably still half full.
We are using the hooks built into the deck to attach a 12L tank under where the seat should be, and it works well, but I can see it may get in the way.
You are right of course that it would be very hard to keep an eye on how much is left.
Like the layflat hose idea, we have a volunteer Firefighter at work who may be able to come by a few feet for me to have a play with.
Could turn up some nice ally endcaps in my lathe.
Perhaps a project for the cold months later this year just to see if it can be done.
RIBBED For extra pleasure.
Member of the ebay Blue RIB cover club.
Member of the Bombard 380 Aerotec club