The ball mount fits easily on the back,  you have to clear your steering, I set mine at about deck height.   I have not tried the more recent mount.  I have the torqeedo 403,  on my Mill Creek 16.5 with sail rig.  more then enough power.  

Daniel,

3 words - PICTURES! PICTURES! PICTURES! :-)

Laszlo

   I don't have pictures right now.  My impression is that the 403 is more power then one needs.   I did have difficulties controlling the power.  I did think about mounting it on the steering but then you have to work harder to keep it going straight. By mounting it separate you can set it to push straight and then steer with rudder.   Also reverse is also hard to control.  Everything has a learn and adapt curve.  If your interested still in a couple of months I might be able to take pictures of the motor mount.  I think it will vary by your steering system.  On one of my kayaks I had to mount it off center to be out of the way of the rudder.   I kayak miles from port and have the motor for emergencies if I have to make it home.  I don't use it a lot inshore. Not much need.  Right now I am on lakes that are no more then a couple miles across.  So I am not using it. 

   I don't have pictures right now.  My impression is that the 403 is more power then one needs.   I did have difficulties controlling the power.  I did think about mounting it on the steering but then you have to work harder to keep it going straight. By mounting it separate you can set it to push straight and then steer with rudder.   Also reverse is also hard to control.  Everything has a learn and adapt curve.  If your interested still in a couple of months I might be able to take pictures of the motor mount.  I think it will vary by your steering system.  On one of my kayaks I had to mount it off center to be out of the way of the rudder.   I kayak miles from port and have the motor for emergencies if I have to make it home.  I don't use it a lot inshore. Not much need.  Right now I am on lakes that are no more then a couple miles across.  So I am not using it. 

   Yes pics would help. Don't see how you'd mount that with a rudder also.

Thinking about electric drive for my MC 13 w/sail rig. I've seen some that mount off to the side thru the hull??? Have you looked at these?