looking cool, be interesting to see how you work the poker hands. I am working on a cribbage themed homebrew where the scoring is cribbage hand based, banks of drops for hands as well as some rollovers for the smaller banks, also with a roto-target for the turn card.
I too printed out at staples, I just taped mine on then used a small drill bit just to mark all the center locations then removed the paper to do the actually drilling and routing.
I really liked your mini flipper ball save idea, but understand the slope issue. how about moving the mini flipper down to under the apron near the center so it would shoot back up between the flippers? hope that makes sense. make it only active for a couple seconds after a outlane drain if qualified or whatever.