Well believe me I don’t only do big boards and guns I have used these numbers (varies by length) on boards as short as 5’ 9" so not strictly limited to the bigger board.
You quote numbers of 10 1/2" and 11" without telling us what the base length of the fins might be, but lets just assume that it is the standard 4 1/2" then adding that to your 11" we get 15 1/2" which is almost exactly what I would use for lets say a 5’ 9" for arguments sake. So as I said before I think you are not interpretting my numbers correctly, if you are reading the leading edge position and then subtracting my standard base length (4 1/8") then that back measurement might look further forward (3/8") than you are used to seeing. So without know the base length you are using it is hard to tell what your numbers mean, at least to me!
But the bottom line is does it really matter, you have numbers that work for you and I have numbers that work for me, the main difference is I have been willing to share my numbers with a lot of different people and they seem to have been able to make them work for them.
At the end of the day all that matters is what works for you. The numbers that I use and share are strictly based on my experience with a very large number of boards through a very wide range of lengths and styles. I do also advise people that the numbers are intended as a guideline but they are backed by solid experience, not something I pulled out of a hat!
To clarify normally I use 4 1/2, 3 1/2, 4 1/4, 4 3/8, 4 and 3 3/8 bases, in an smaller % I use other base dims on quads.
normally on 5 9 s the front fins are onto 10 3/8 - 10 1/2 range if to that I add for ex a FCS 3000 (4 1/4 base) we have a total of 14 3/4 or less!
The .pdf looks like a 6´board that goes up to 16 if I remember well and then more with 6 1 etc,
Seems that in the 5 9 more than 3/8 and in the others even more
Anyway, what looks too forward for me is put the rear fins at 7 1/2- 7 3/4 back edge (11 leading edge) on shortboards.
but as you said, works for you, for me also looks too forward in a HP shortboard and I still maintain that I need to tweak the tail rocker to compensate for that among other things.
Good to discuss with you due to your experience there in Hawaii.
Im not guessing too, also I noticed long time ago, that with my kick tails on modern mini eggs, too forward do not hold the boards and lack of drive a lot
I’ve used Robin’s #'s as a guideline for a shortboard (6’1") and a quad “fish” (5’9")…
the first shortboard was converted from a McKee setup to Robin’s #'s and went WAY better! The change was AWSOME! the usual rave: “faster, looser, more drive, blah, blah, blah…”
the “fish”, in quotes because it’s a diamond tail, belongs to my brother. I’ve never surfed it but he likes it. He’s somewhere between beginner and intermediate ability. He can trim and turn/cutback.
I suspect that the distance from the rail of the rear fins is different between Reverb’s and Robin’s #'s.
Hey Cris-- just to throw my two cents in on distance off the rail; I usually wind up with 1" ---1 1/4" or even 1 1/2" of the rail. Varies due to the shape/template and the toe that I want.