Glad you liked Bob's models, I'm finding his models absolutely delightful to build myself.
About mounting the brick in one of the booms, I think it's quite doable (the idea of linking the two rudders together with a rod at the trailing edge has worked very well for me in the past http://www.rcgroups.com/forums/attac...mentid=4270483
), but I would worry about fitting the brick into the boom and even more, about battery placement possibilities (extending the leads could help solve that problem, but only to a certain extend). In any case the lateral CG will be out of ballance, at least by the brick being heavier than the single servo, each in their boom, if not also by the lipo being closer to one of the booms.
Do you already have the above mentionned AR6400T?
If not you could consider using any other AR-brick (why not one with no onboard servos, total placement freedom! Then you could mount a servo in each boom, one for elevator and one for rudder). Their esc can handle up to 2mah, which allows for two UM Cub J-3 motor/gear./prop.'s (they draw appr. 1,90mah together), driven by any lipo from and above 120mah. I believe to remember that with this setup, there's somewhere around 40g of thrust (this needs to be verified, I couldn't find the info again myself)...
PS If you feel tempted, give Bob's plans a try! Either in paper (first?) or...
In the case of my Grumman Albatross, I pretty much constructed it as if in paper, but calculating the extra thickness of the 3- and 6mm Depron and the 3mm Epp I used.