if someone gets better primary than this i'll be VERY impressed & surprised, i don't see how it could POSSIBLY be lower.  this solve doing both projections on the same cycle is suspicious, but i don't think the leaden sea can be made any faster.

i can't see how i'd do this any cheaper, but the opus magnum community's done some wild things so i wouldn't be surprised to see it.

found a 2 area save from my last solution (not that it'll matter)