Hi Dennis,
To tell the "whole truth, and nothing but the truth", this is the first TWIN I hav really been interested in to want to actually build one!
I have always, ALWAYS, wanted a twin engined stunter. But the closest one I have considered so far is Jack's Mosquito. But it looks very time consuming on the plans.
The Sky rocket, on the other hand, looks a LOT simpler!
Two OS FP or LA 25s or Brodak 25s would haul the mail as well as the Foxes, thought maybe not with quite the same "run" characteristics. Two OS 25Fs would be a LOT more power.