Right at a month ago i replaced our rear Sypinergy wheel with a HED 3 wheel. I had to modify the rear of the frame to receive the wheel but that was fairly simple to do.

We have been using a HED3 on the front since the middle of January and I have wanted a HED3 for the rear but had not figured out how to modify the rear drop spacing until recently.

The ride is a little firmer but dropping the air pressure in the tires from 120 to 115 has made it ride just about the same as before. Our average speed has gone up between .50 and .75 MPH, it is really amazing, we both notice that the big difference is when we ride in a cross wind. The bike looks really good with the matching wheels. I am going to order another set for my solo bike and they will be the backup wheels for the tandem.

Here is a link with pictures and how I modified the rear of the frame. http://www.bikeforums.net/showthread...front-and-rear