A little halyard trick
You don't need to drop the mast. Make up a small line (1/8 inch cord from the hardware store, 100 feet long). Sew about three feet of small chain (also about 1/8 diameter) to one end of the line. Go to the top of the mast in a bosun's chair (on the genoa or spinnaker halyard). Hang this cord outside the mast until the chain is hanging at the level of the main halyard exit hole in the mast. Mark the cord at this point. Then haul up the cord and feed the chain into the sheave box for the main halyard. Let gravity pull it down through the mast until you reach you mark. Now have an assistant fish around for the chain with a short piece of wire, needle nose plyers, etc. One the chain has been pulled out, you can tape you halyard end to the end of your feeding cord and pull it through. It's really not that hard. The worst part is going up the mast. (Most docks have a young ape that enjoys doing it - if you don't.)Good luck!