I have several boards (all made by him) with Harbour’s nose channels. They work great, IMO.
When you’re trimmed a cross-step back from the nose, they work like an accelerator pedal as you weight/unweight your front foot. They especially do this when you’re “pig-dogging” hollow waves backside. What they DON’T do is push water and slow the board down (making it kind of hydroplane or “float”/stall the way “soft” nose concaves do on some dedicated, “nose-rider” designs I’ve ridden). They also do not cause the board to be at all “tracky”.
I think they slightly reduce swing weight as well and help the board to plane earlier when you’re taking off. But I’d say that’s more a subjective call, since I haven’t ridden otherwise-“identical” boards both with and without the nose channels (which would be a more “scientific” way to determine how true that is).
I won’t pretent to understand how they interact with or are complimented by alterations to other design perameters of the board or exactly how they blend into the overall bottom rocker. On a 9’6", I can first feel them start fading in (at the rail) at about 7" back from the tip and they seem to fade out about 40" back (again, by feel).
I know he’s been using them at least since the early '90s and has tweaked the design slightly over the years.
I started making boards in 03. My first one was 9’6"x22 1/2"x3" with my rendition of Harbor nose channels. the first time I took it out I was amazed! It floated! and it paddled great! But when I moved to the nose it slipped all over the place. So, I made another one exactly the same dimensions and shape but with a concave nose. It was SLOW! What a DOG! So I went back to the nose rails, learned how to control them and never looked back! I love 'em!
Every board (almost) I’ve made since (27) has my rendition of Harbor’s nose channels (nose rails?) After the third board I changed (thanks Bert!) to balsa composite construction. The rails now are 1/8" balsa sheet laid down on the rails, 30" long, tapered from 2 1/2" to a point about 7" from the nose. The inside edges are parellel.
Somewhere on the Harbour website, the noseriding channels are discussed and explained on why the original design was changed. I believe they give all dimensions of the channels.