Maybe I´m a fool, but I would be very pleased to have the model fly as much as possible like the original... And as far as I know the fullsize also has huge amounts of prop torque to deal with... So I guess that it will be the ultimate scale experience.
Based on your replys I think I will make the reduction drive at a 4:1 ratio and make up a 33,6x37 4-blader, and test the combination on an old towplane first. Just to see if it will fly at all.

Thanks