In my estimation, it would be impossible to supply enough force to a slide without going over the foul line in this set-up.

Not like it's an issue, since you could just say there IS no foul-line with this interesting set-up.
I think a more playable layout with 8 boards would be to have each of the 4 players have a double-length board, though. It would increase the difficulty and skill required, but still be playable.