On Saturday, June 7, 2014 8:39:45 PM UTC-4, Cookie wrote:
... better prototype uses a clear plastic 5 gallon water container....really cheap...works great with compressed air from a tank...lifts you easily 9"...brings the butt about level with the gunwales of the Grob 103..
2Ck%3Acollapsible%20water%20container

That's a clever idea. There are many types of collapsible/inflatable water containers available. Which type works for you?

http://www.amazon.com/s/ref=nb_sb_no...er%20container

We had two mid-80's age glider ride patrons last weekend and even though they were lightweights, getting out afterwards was hard. For occasional use, the airbag approach might be easier to implement than the more elaborate alternatives, and the price is right (the lift bag that I linked costs 100's of dollars).