That CANT Z is certainly a great looking project. Sorry Paul I know nothing about that airplane but you did ask for comment on the use of small outboards on a triple.
I have done a number of twins a triple and a quad. And the loss of an engine on a twin is far more tramatic than a triple or quad.
Its my feeling that doing the mixed engines thing on a triple is not really neccessary and that out thrust on both wing engines will provide that controllable edge. Another is a rudder gyro.
Another down side of the mixed engines and switch throttled outboards is the airplane never sounds quite right.
John
