Thad,

yes, the pente-x idea is good. I was thinking that to make it easy you could prove a win on as small a board as possible and the win would still (effectively) be valid for any larger board -- assuming that p2 moving farther away would not be beneficial. Of course that assumption is not perfectly valid...

Generally it should be easier for p1 to win on larger boards because the attacking lines are not as restricted. A win on a small board with chosen moves for p1 will not necessarily show the fastest possible win. I will try some searches on small boards.