Hi Jay, welcome to the Mainship world! I have modified my 2003 390 mast to fold, choosing to add a hinge plate assembly between the mast baseplate and the deck. There are no mods to the mast required with this arrangement. The hinge consists of two square aluminum plates, hinged at one edge, with the lower plate attached to the deck with the original screws and the upper plate drilled and tapped to match the mast. Where the two square plates extend past the round mast baseplate, there are studs threaded into the lower plate and matching holes in the upper plate. I use two knobs to clamp them together. The hardest part of the project was releasing the bond between the baseplate and the deck (a few hrs with a paint scraper finally did it). Sorry no pictures (boat is still shrink-wrapped), but I'd be happy to post some soon. The guys who do my shrink-wrap love the arrangement!