Martin,
I have made a shear legs for my Corribee 21, and it has made launch day a lot easier. I use an icicle hitch to grip the tapered mast.
I used some old carbon fibre windsurfing masts, which worked brilliantly and are very light. Recently, I added a couple of feet of steel tubing - it just so happened that tubing from my local agricultural co-op (as used for cattle crushes) slid nicely into the masts.
I don't stow the legs on board, but it would be easy to do so.
I found the following links very useful: Freedom 21 shear legs, Freedom 21 notes
For a small boat like mine (I can float her off the trailer) I highly recommend making up a set of legs.
Declan.