Wondering whether there's a tried and proven rule used by anyone to position the rear footstraps relative to fin positioning, specifically for weed fins used on smooth water speed runs?

Board is a 57cm wide narrow tail slalom using either Fangy delta (FF1) or 45 deg weed speed fin (Tuttle).
Rear straps have 5 hole positions whilst front straps have 4.

Have an old copy of JP Aust guidelines for foot strap positioning, counted from tail (with same spacing common for all other rows of holes) which states:
1st hole: direct > "speed, radical maneuver"
2nd hole: recommended > "best overall performance"
3rd hole: easy allround > "controlled performance"
4th hole: reserve > "easy control"

I've usually followed this guide for either upright, raked or weed fins and go for the 2nd hole (if there's 4) but think that when using weed fins (particularly deltas) that the forces in play are very different to the norm, so curious to know where others usually position their straps??? (especially the rear ones).

The easiest way to figure that out is by just trying the different positions on the water. Leave your screwdriver on the beach and move the straps after a few runs intil you have found the sweet spot for your sail, fin, and board combo.

While some people might have guidance, it can be different for your setup, conditions, weight , stance, and personal preferences so it's best to experiment. Also the hole positions on the one board/brand are not necessarily comparable to another.

The general rule I have found to work for me is footstraps as far back as they can go with highly raked weed fins.

The reason is that the Centre if resistance is further back with a high rake weed fin on most weed fins, even if they have a bit of front overhang from the box. I move both the footstrap and mast base back to keep the balance.

Of course, your situation/board/fin/sail may vary.