Mike,
I'm glad I wasn't being seen as rude and that as a designer you already know that centerline of pipe is as key to pipe layout as the keel plane of a boat! Everything depends on an accurately drawn or designed centerline to run pipe (I used to do pipe design for oil and gas offshore here in the Cook Inlet, in SC Alaska; ANSI 150, 300 & 600) and the keel plane is only displayed as a shape in the Profile View! (otherwise it's just a vertical [body plan] or longitudinal line [plan view]).
Dave Gerr, a marine architect on the East Coast (
http://gerrmarine.com/) has some great books out and they're worth their costs to your project. I've even purchased multiple copies at a huge discount by using the online book seller (
https://www.alibris.com/ ) so I could give copies of his books to friends and students affordably.
The Nature of Boats is a great read, and worth the
list price on Amazon!
Another marine design and wood builder Sam Devlin also has a few books out that explore the hard chine lines of sheet material boats. In his books there's a fine discussion of lines and modeling that are helpful to visualize the design considerations involved in your project.
While I've only installed two Arneson style drives in one boat in all that I've built... I do understand they require some provisions not seen in other drives' hull shape requirements. However, I'm not conversant in the required design elements as they'd be realized in correctly drawn hull intersection lines, and I'd say that discussion would be best held by contacting anyone who builds the drives for sale, anyone who's done some hull mod's to install these drives and owners or operators who drive boats- driven by these drive systems?
My (initial) primary concern is that you understand (explore and evaluate) the shaping implications of
rounded/curved/swept Buttock Lines (actual "rocker") as compared to an
'angle point'/hogged/raked/kinked Buttock Line change; in adding your 3' hull extension. Any hull extension to a planing boat could be a Profile View - flat, straight and level extension to the exiting hull (ignore plan view ['width'] for this consideration) or it could have Profile View (elevation view) that is rounded as the Buttock Lines rise in curves aft.
In general, while the Arneson's may benefit from some degree of rocker in the Buttock Lines aft?? That point must be explored very exactly to agree with the person who's asserted this claim.
Another point to make in regard pitching the bow upward, semi-permanently, is that the running waterline will move aft to amidships and this hull's V/deadrise/angle of entry gets very significantly less as the waterline moves aft! (5 deg. at the transom is essentially FLAT) Therefore, the 'ride' will become more and more 'rough'/HARD/pounding in any kind of chop or waves, since the angle of entry is moved to lower deadrise and flatter hull sections. Not sure of your area of operations or water conditions; but the only angle by the bow this hull will ride 'smoothly' is when the bow's pitch is low, and the forefoot is used to enter the seas- regardless of how tall or short they may be?
Please let me know what I could help discuss as you plan your project?
Cheers,
Kevin Morin
Kenai, AK