I always see the T guys not using the tiller when they fly the spin. Why is that? wouldnt you want the ability to move around? doesnt this restrict your possition on the tramp?

1) Holding the tiller extension downwind puts it square in the nuts of the guy on the wire. <img src="http://www.catsailor.com/forums/images/graemlins/blush.gif" alt="" />
2) It gives you better rudder control. Steering directly from the tiller crossbar eliminates any flex / slop in the tiller extension.
3) If your're going downwind with a guy on the wire, your butt is parked in the back of the boat. You don't need or want to go anywhere.

...so it is probably more applicable to being 2-up, rather than 1-up. I found it helpful on the Spitfire, when it's that windy that you know you won't want to go forward, but I don't recall doing it on the Shadow (solo), when I am more likely to go out on the wire (with the stick!) if the breeze picks up.

Also, some T tiller extensions don't telescope or are just a bit tricky to telescope...so making it smaller and not protruding into the trapzeing crew is not worth it.

I use a non-telescoping extension (from an Acat). If the I'm holding it and the crew slips on the trap while downwind, the tiller will be snapped in half.

The rudder crossbar will also give you something to hang onto in a pitchpole to keep from going forward. You can usually save it if you can keep at least one of your weights back. If you're hanging onto the tiller, it just pivots as you slide down the launch tube.