On Monday, February 10, 2020 at 5:06:29 PM UTC-8, wrote:
Hey Bob, did you consider using one of the wake board ballast bag manufacturers? They list a custom option usually with prices starting at $100. I haven't called but expect to use the old bags I have for a while.

I considered several local makers of pond and tank liners before going with Streifeneder. The money saved didn't seem worth the time and risk. When I started developing sailplanes, I decided that there were several technologies I would leave to others, and ballast bags became one of them. The other big one is acrylic transparencies.

--Bob K.