Piston problem solved, in the most trivial way – I shaved down the sides of my MDF piston heads by 1mm, then I use a piece of vinyl fabric glued on top as my powder seal.
Currently printing my first calibration object – I still have some sequencing issues, it seems – my fuser pass needs to occur before I lay down the next powder layer!
All in all, a good day!
I’ve moved my project page to http://reprap.org/wiki/BrundleFab on RepRap.org, as my personal site doesn’t have that much image storage space.