Sadly not documented. (I didn't think it would fly -- that'll learn me.) I bought my tank and brought it to the studio. The tank is about the size and weight of a large scuba diving tank. Mylar balloons don’t hold the helium (or at least the cheap ones I have). I made a test and inflated a balloon and to hold it down I used some wire I had and twisted it around one of the smaller clay tablets. I then added two more balloons and oh my didn’t I achieve neutral buoyancy. I didn’t document that auspicious occasion but I did make a short video of the clay and three balloons a little later. There was sufficient leakage out of two of the balloons so that it no longer could hold the tablet suspended but I can re-fill them later.