Thanks for the advice Brian. The plan right now is for the generator and 2 house batteries at the transom. Below deck he would like 2 ea 100 gal fuel tanks that will start about 12" forward of the transom going forward, then a small water tank. (I've not calculated if there's enough room for both fuel tanks to be 100 gallons). I think 150 gallons of fuel would be plenty and expect at least 3 nm / gal from this boat at cruise. It'll be powered with a pair of 2007 mercury 4 stroke 150's that have 100 hours on them. They've been pretty much pickled and appear brand new.
There will also be 3 batteries for the spot lock trolling motor somewhere midship to forward up to the front pilothouse bulkhead.
I've put a lot of hours on my 27' Jumbo and believe your advice to be perfect for someone building a Tolman also. I've noticed a huge difference in fuel mileage and performance by making small changes like moving a 100 pound life raft from the cuddy to around station 6 in the pilot house. I know you made a completely new plan for the GA, but there are enough similarities between them in construction material, weight, etc. I made many trips offshore in the NE Atlantic with a 500 pound tuna cooler sitting 3 foot forward of the transom and an extra 300 pounds of jerry can fuel in the pilothouse. (LOL... those were the 2 stroke days as there was already 87 gallons of fuel in under deck. ha ha)
Sounds good, although the 3 batteries in the house, possibly as far forward as the forward house/aft cuddy bulkhead might be weight you could keep closer to the aft house bulkhead. And as far as boat similarities go, I was and am very impressed with the structural design of the Tolman, and that's why I used it (with Renn Tolman's explicit written permission) on the GA ... if something's optimal, then it's optimal ... don't reinvent the wheel. And also, all planing hulls are very similar on where the center of gravity goes, and that impacts loading decisions. Unlike a displacement vessel, planing hulls have a list of requirements that make them able to skim across the water efficiently ... more akin to an aircraft needing to be balanced perfectly versus a car rolling down the highway that can be loaded pretty much any way you want ... not so on airplanes and planing hulls. Two thirds of a planing hull is forward of the center of gravity, and like a teeter totter, you must pay attention to loading in order to keep things balanced and operating optimally.