Alan,
I am puzzled by your comment "Two separate power source's for the Shack Contra Prop"
We took apart a very old Griffon 58(to see how things worked) and the simple answer to the two power sources are a set of differential gears that fed of the front part of the crankshaft, that in turn fed one big power transmission shaft which was the rear prop, with a slightly smaller and longer power transmission shaft running through the larger one to power the front prop, all this superb engineering was what could be called , very accurate but very steam age and bordering on the agricultural in size of gears and huge ball and roller bearings, according to the RR people I spoke with to get detailed drawings for said engine the power division was equal, looking at the gears and shafts it really cant have been anything but equal.
P R-B