I have a ZN integral and I had to mount it on a plate located just under the gear plate, inside the fuse. You can stretch the plug wire until it reached the landing gear mount. If you mount it next to the pipe, the electrical wire to the crank case will be short. If you mont it inside the fuselage like I have, the plug wire is shorter as it will go from the top of the engine and down before it goes inside the fuse. With the Hatori pipe and nishioka mount the area around the pipe is pretty crowded so I didn't have room. I have retrofitted CDi but if it had been considered when the plane was in kit form I'm sure you could fit it in the pipe mounting area just ahead of the gear, on the side of the muffler.

Here you can see the muffler area: http://www.flickr.com/photos/aerowold/4234692386/
Here's the inside of the fuse. It's not visible but I have mounted the CDi unit just ahead of the tank on a separate ply-plate.
http://www.flickr.com/photos/aerowold/4233921461/

There's also a questions of orientation. The plug and wire exit the box on different sides so if you stretch one of them as far as it'll go the other one will be much shorter. Mine is mounted across the fuselage so both wires are as long as possible. The easy solution would obviously be to lengthen the wire to the crankcase.