Hey, go for it! You might want to go ahead and cut/join the two cranks before you finalize dimensions. On the BME twin that I built I had to work at it a bit to get the mated crank parts short enough to fit into the BME case. Might be a good idea to make the case slightly oversize and use shim washers at the ends of the crank.

It will be interesting to see how this turns out.

Good luck,
AV8TOR