I have an '87 272. I used the yard's crane to step my mast. Since they did such a poor job this last haul-out, breaking my mast base and all, I am considering stepping my mast. I lowered my mast when I bought the boat by using an A-frame. Oddly, there was no forestay on the boat. I think the PO removed it to store the tuff-luff he had on it. I found it stored in the boat later.
Anyway, I had two halyards which I connected to the A-frame, and I ran a line back to a cockpit winch. I lowered it nice and slow, stopping to check shroud turnbuckles and all. I had a crutch to rest the mast on in the cockpit. It worked ok... The halyards created uneven support, and that torqued the mast until one of the 2x2, a-frame supports broke. The mast fell the last 1-2 ft. Scared the s#%t outta me! No structural dammage. Only the anemometer cups broke. No biggie. The yard did more damage with the crane this Fall!
I think an A-frame will work as long as you use the forestay. I would make that A-frame of metal, thank you! Also, a 10 ft, telescoping mast crutch would be awesome. If you really wanna work it, mount a winch on your trailer to give you more control and side supports for the shrouds in order to stabilize the mast left-to-right.
It is a big mast! I use a crane at my shop to lift it off the boat for storage in the Winter. Let's exchange pictures of our plans here in the Spring.
I sure hope you post first, so I can copy your design. Since I will basically be stepping it single handed, wthe the exception of the admiral, who will put in pins, my design better work!
Thanks,
Andrew