I used to tie the wing on an X-caddis like the wing on an EHC. I now tie the wing a bit shorter on an X-caddis.

I've talked to Craig Mathews about the X-caddis. Craig Mathews explained that the X-caddis has a shorter wing than the EHC. He says that you can tie it as long as the shuck but I do not. It is an emerging wing. I can't prove it, but I personally think that a shorter wing indicates an insect in an earlier stage and more vulnerable to the fish. So if you are going to make a mistake in wing length, better to it tie it a bit shorter rather than longer.

Take a look at the link to Dave Hughes book below and compare the wing length on the EHC (flies 1-4) in the photo to the X-caddis (flies 5-6) to see the difference.

Essential Trout Flies By Dave Hughes

In the video below Craig ties the wing as long as the body. Notice how short he clips the shuck.

http://www.youtube.com/watch?v=QvCw0DrINS0

Hans Weilenmann also does not tie the wing on his CDC and Elk beyond the hook bend.

http://www.youtube.com/watch?v=NJyIbgKYHwY