UTC - thanks, I really appreciate the insights, along with your design knowledge and board-building skills from scratch

Surprised by the outlines - I'd thought the red board was much longer.
I still wonder whether there's something useful to explore with a longer board, carrying more length through the tail and with the foil tracks positioned more centrally, similar to downwind boards.
It probably wouldn't pump very well, which is fine with me, but intuitively the glide should improve if we can stop it from feeling sticky or "sucky" through the water.
I've also thought about building a simple board from XPS foam. The closed-cell structure would suit a rougher, more practical build style, which works for me since I've rarely had a decent build space.
Good idea using a hole saw to reduce weight.
My "workshop" while installing the tracks in the FoilX - Mark Oz was just making one of his lame jokes

when he said I was in W NZ. I've moved to Hobart, Tasmania