A 2 part silicone such as Sylgard would be a much better potting compound. Also since the black cells will heat much faster than the front glass, a very soft silicone is preferred over caulking type silicone to prevent cracking due to thermal expansion. Also if there is an impact or deflection of the front glass, there is less chance of cell damage with the softer silicone. We have large hail here so I have been hesitant to use any design which places in contact with (or bonds) the cells to the front glass.

   My plan was to bond the cells to the rear glass with a dab of silicone in the center, leave some of the tile spacers in place to support the front glass, put in some desiccant seal with silicone.

   I will be watching your thread and hopefully you will have some results by the time I actually build mine.

Mike