Not sure that preventing air circulation is a good idea, usually it is recommended to ensure as much air circulation as possible while keeping all water out. Also dehumidifiers while they do a good job, have been known to catch fire, and at which point your insurer might wish to argue about liability.
For long term storage, and knowing that Bavs have a tendency to leak water through deck fittings etc., I'd be inclined to have the mast taken down and laid horizontally across the top of the boat where with the spreaders and valuables removed it can be used to support a tarpaulin over the boat. I'd also drop the guard rails and take out the stanchions so that the tarpaulin could hang over the side without wearing through. The tarp., could be secured under the boat, and its presence over the boat should prevent water leakage via the deck fittings. Keep the mast valuables such as aerials, tri-light, wind transducer etc., locked away within the cabin. Keeping your boat dry inside is important, but allowing air to circulate to prevent mould is also important. However my boat is not in Florida where you have occasional hurricanes to contend with so you need to minimise windage and ensure your boat is very securely tied down. For boats kept in the Mediterranean be aware that it can get very cold indeed over winter such that you should consider precautions against possible freezing.
