Ok. I would really want to build a top down printer as well, but the warping issue, have me wondering if I should.
This is just an idea, what if the build plate was heated up to a certain temperature, like a submersible heat bed being installed on the build plate. Not sure if this would work, and how it might affect the resin. one thing for sure the resin might become less viscous, not sure if it will solve the warping issue.
Here is a low voltage pump, I think this could work: http://www.ebay.com/itm/201087635665?_t ... EBIDX%3AIT
It's a Peristaltic Pump, I think Pacman used this to fill and empty his vat!
Let me know what you think!