It occurs to me, that since we are switching the laser on and off successfully, that signal could also operate a small solenoid to dip the print. So that laser OFF dips the print 2 - 3 mm and then laser ON returns the print to its former position. The solenoid would move a print platform down and then back up, in synchronisation with the laser (there's probably enough power with the existing 10 amp FET, to use the same output FET, so no extra components required). This would allow each layer to be well exposed before doing the next and reduce a lot of the calibration problems. So the laser would make maybe 10 transits of the current z, laser OFF (solenoid OFF) then dips the print, laser ON (solenoid ON) then returns the print to its former position. The laser will obviously have to wait for any ripples to die down, before carrying on. The solenoid would obviously be positioned on the outside of the tank and could just tilt the platform via a plastic lever, to allow wetting of the print surface. This is quite easy to design mechanically and would be analogous to the form1 tilting tray (used to tear the current layer off).