I think most of us have the stern crutch Craig describes below. I made a replacement for mine. Not too hard to do. I also added a forward trailer mounted carrier. It is square metal tube, welded to the frame, and mounted just in front of the winch stand. It has a U shaped bracket on top, and a V shaped bow stopper bolted in for the mast to rest on. I also welded some single chain links at the top to hook those heavy rubber tarp straps to as tie downs. And at the same time I added an outboard motor bracket. Keeps the weight off the transom, and motor out of the car. To find a pattern, crawl around in some boat yards. Lots of the trailer boats larger than ours have mast crutches to study and copy. Howard
On my '84 17', I don't have a trailer-mounted mast-carrier: I just rest the mast on the bowsprit (protecting the stainless tubing with foam padding) and tie it securely for transport. For the stern, you should have a heavy-duty wooden crutch designed to fit into the gudgeons (Or is it pintles: I always confuse the two) for your rudder. I'm pretty sure Nor'Sea still uses the gudgeon-mounted crutch and you can verify by going to their website www.norseayachts.com and looking at their pics of a Monty being prepped for delivery. My crutch has only one height, for trailering.