I experimented with this with the Candlewic Container Palm and found I could go up to about 7.5% Soy without losing crystalization. I also got really inconsistent results though, cause I was using a melting pot. Might be a heck of a lot better now that I'm using a Presto. But another problem I had was leaking of the soy out of the Palm, just like as if you put too much FO in. I have yet to experiment with Glass Glow, but am anxious to do so when they get it back in stock. For the very reasons you discuss above (hang up and lack of glass adhesion in a straight sided glass). If you get to testing this before I do, I would LOVE to know your results.