Lowering a deck stepped mast.
I raise and lower the mast on my O''Day 26 every year. Your mast is probably significantly heavier than mine. I always use a crutch as Jeff has suggested. I tie off the jib halyard and attach a looong boom vang to the halyard and the stem head and lower away. At some point the guy on the vang cleats it off and the stretch in the line finishes lowering the mast. You''ll know when you reach the point. On my boat 2 people can accomplish this feat with little trouble, a furler requires one more body. Your boat being on jack stands would make me nervous but only because I have no experience with boats on stands. I think if you can find 3 more good strong assisstants it''s a doable deed. I normally don''t have to loosen shrouds, I think that depends on the rig.