This could work

[Anuvin]

I think I see where you are going with this idea, and I do like it, but I am having a hard time conceptualizing it. Any chance you could doodle up a design?

[mike_biddell]

I think I see where you are going with this idea, and I do like it, but I am having a hard time conceptualizing it. Any chance you could doodle up a design?

two cylinders nest into each other and are sealed with an O ring. The top cylinder orifice is to allow the cylinders to be full of saline and is closed when printing starts (using a small bung). The shaky rectangle on the top cylinder is a weight. You simply pull the cylinders apart until the top cylinder just touches the resin, then close the top orifice. The platform descends, expelling saline out of the bottom orifice, back into the tank. The descent of the top cylinder for a given orifice size and weight should be reliable and reproducible, as long as the O ring is not too worn. Sorry for the rubbish sketch.