It would be helpful to see what you are trying to put this in. The Dynamax needs a pretty long thrust tube to work well. For a swamp boat type, you may want to go with a pusher prop to give you the torque to get going. If you really want a ducted fan, I would look into the Byron fan since you will have more thrust where you will need it and it isn't as critical when it comes to thrust tube design.

Good luck,

Mark