Uh, Westinghouse motor and a car battery?

Thanks, Keith! That’s a tremendous help – I’ll use this as a starting point.
 
FWIW, I’ve been fascinated with Big Jim’s El-Jay since I first saw it as a kid in 1982. Granted, some of those memories may be through the rose-tinted lenses of youth, but I remember seeing some great flights out of various versions of the design built by Windy, Mike Rogers, and Craig Gunder. Yes, they looked too big on the lines, but I loved the impression they made … when they were flying right. And that was usually in dead calm, or a light breeze. In anything above that, the whip-up on them got crazy, with loops looking like a pencil – a rocketing line straight up, and then a line straight back down again!
 
Still, I always remember the good days I saw the design fly. Random musings years later led me to believe that while the design might be really good, the ST 60 engines that they all used were probably the worst possible choices for it. Not that they were lacking for power, but they had that old-school more pitch/4-2-4 break that didn’t help the whip-up. It occurred to me that a more suitable powerplant – a piped PA 75, maybe – along with fully adjustable controls, which the original models didn’t have, might work better. But I sort of shelved that idea and moved on to other things.
 
Reading about the electric motors used by the likes of Paul Walker and Igor Burger, though, got me thinking about the El-Jay again. And I think the accelerometer that their setups use might be even better than a piped engine for it.
 
I honestly don’t think an electric El-Jay is the next world-beater, or that it would be better than something like a Thunder Gazer or an Impact. I am curious to see how good it could be with a modern power system and adjustable controls, though, so I think it’s worth building one. And I’d like to see something that damn big on the end of the lines again.
 
I’ll keep folks posted as I move along on this project.

I got the foam cores for the wing and the stab/elevator from Jim Damerell, along with the side view plans (thanks a million Jim, you’re the best!). In looking at the plans, it looks like the design I have is actually the 72” span BJ, which is fine – that’s plenty big for me. (I have vague plans for making it look like Windy’s Killer Bee or Black Sunday, but that’s still a while away while I start sheeting wings.)
 
For the controls, I plan on using a system that’ll let me easily adjust the flap/elevator ratio and the pushrod length. (In other words, a fairly typical Tom Morris system!) I plan on starting with the throws and ratios shown on the stock plans, but I’d really like some freedom to experiment from there and see what various changes make happen.
 
Thanks for the motor/battery combo suggestion. I’ll keep that in mind as well. Ideally I want to get this WAY under my estimated weight of 80 ounces all up with battery, but I’m trying to err on the extreme side of caution. Having never built anything remotely this big before, and not knowing exactly how much the battery for this monstrosity is going to weigh, I want to make sure if I make a guessimation mistake in my building that it’s “too heavy” and not “too light”.
 
Jose, if you could let me know the flap tip chord length for the 72” BJ, that would be awesome as well. That’s the only design “number” I’m missing.
 
I just ordered some wood from National Balsa, so I should start the build around Thanksgiving.