Yeah it’s very tricky to definitively call one component as the primary driver to “make it easier”, I’ve personally found short and wide to be the worst combo, so then the question is how much does more length play into the stability, vs reducing width. For me the issue has been getting board speed for faster foils, the stability isn’t an issue… so long and narrow it is.
This is a good point. For someone who is 30% heavier I’d expect them to nearly proportionally size up all dims, and so 7’6 x 18" for me at 70kg is proportional to 9’9 x 23" for 91kg? Is it fair to stretch all dims linearly? Probably could do so.
Fwiw, a buddy just shaped a bullet style board, and it was pretty tall, narrow and long. It wasn’t immediately stable compared to my roughly same width, smaller flatter barracuda style SPG board, and the way the tall bullet-esque shape board rolls over feels pretty weird. Once it gets to a certain point it seems to become less stable. I thought this article was interesting in showing some of the engineering aspects to how balance works. Complex stuff.
But the point is that it is not strictly easier, for much more volume, and length. Where it does gain is that it is super fast! That said, within a few sessions it starts to click and then the balance becomes a non-issue, until you get tired.
All this comes down to what the immediate goals are and current ability… maybe a “Cry Factor” diagram?