|I've seen a couple of very similar set-ups. The height at which you store your mast depends on what you want to do over the winter. If you don't need good access to the deck or interior, just place a length of wood across the pulpit and across the stern pulpit, lashed or taped according to preference and rest the ends of the mast on these. Build a simple little cradle that sits on the mast step and supports the middle of the mast; it should be just high enough to keep the mast straight and level. People here use 2"x4" timber for this because it's cheap and available; I don't know what the European equivalent size is but I'm sure there must be something in that range. If you want access to the deck or interior, bolt two pairs of 2x4's together in X's, making them tall enough to give you the height you want. Stand one up at the aft end of the cockpit, the other around the aft end of the pulpit. Build a cradle for the middle that keeps the spar straight. That's it.
C&C 27 Mk IV