Congrats on getting started on your boat, Ed. This is the fun stuff!!
You're looking at the Broadbill, correct? Some of the responses made me wonder if you are looking at the Bluebill....
Anywho, I lengthened mine by a total of 4" to an even 11'-0". I did it by simply adding 1/2" to the normal 12" spacing of the lofting stations. I started at the transom and worked forward, that way the bow lofting station positions were not affected at all. The cockpit grew a nice 6", by simply adjusting the fore and aft bulkhead positions slightly, (each by an inch) and with the additional 4" of stretch.
I added about 3/4" to the top of the bulkheads to add more rounded curve to the decks. I did not adjust the side heights of the hull, as I didn't think of that. I wish now that I had an extra inch, as I would like the extra storage under the decks. (not a big deal on the side decks but it is for the fore and aft storage...)
I would not add more than 2" though. Probably only 1.5" would be all I'd add. And another reason to not go too far, you would need to be careful about too much height added, as that could effect the distance from the top of the transom motor mount to the top of the aft deck. You could potentially run out of motor tilt clearance.
Depending the size of battery and gas tank you plan to use, you could get both under the foredeck, (or not, if they are too large) and the weight up front would be fine. I'm always try to get all my gear to the front. My boat is stern heavy with the motor, me and the dog (she HAS to sit between my legs) so I think distributing weight up front is ok.
This is fun stuff!!
Good luck to you.
Best,
Brian F.