I'm still making some slow progress. I'm still experimenting with the design of the mold for the rolling diaphragm seal. I haven't managed to get the result I am looking for just yet. As for the attachment of the seal to the housing, I am now thinking about using some type of snap ring to exert a constant pressure on the walls and create a seal like that. But since I'm waiting for a new order of silicone rubber to arrive up here in the Arctic, I started experimenting with the design of the mass shifter section. I thought it would be easy enough to simply use NEMA steppers for both roll and pitch. I found this cool herringbone planetary gear which would do well for roll mechanism. 

After printing and putting things together and some testing, it seems llike the NEMA steppers won't have enough torque to do the job, at least not reliably. So I will probably move to geared DC motors and potentiometers.