Brian,
I have an older E26 and I use a Yamaha 6, 2-cycle that sets down in a well. It moves the boat at about 5kn without sails and if things are just right I raise the main and can cruise along at 6 to 7.5 kn with an occassional burst to 8 kn. Disadvantages are that I must lift the motor out of the water as often as is possible to insure the fresh water flush. The 2 cylce is light enough to accomidate the lifting by one person. I understand that 4 cylces are a bit heavier. Here in California, it is also my understanding that 2 cycles are getting harder and harder to come by (because of air pollution laws).
I am concisdering changing to the transom the same as you are and I would be interested in hearing other pro and con opinions on this topic.
MY concerns are several but here are just a couple:
1. Would my docking ability be more manuverable with the motor back behind the transom where I would have more swing? It is restricted when its down in the well.
2. Am I going to be able to reach over the transom to handle the engine while the boat is moving and still be able to see where I need to go while docking?
As you can see 90% of my concern is docking. I think unerway in open water the handling of a transom mount would not be too dificult.
attached is a photo of the tiller and attachment and behind it you can just see the motor. I think I have some better photos somewhere on a disc. I look for them.