I've got two halyards, one for the
jib and one for the
spinnaker, so I have to drop the jib off the
furler (big PITA) to free up its halyard to use for the lift.
I I have a spare sheave and mast opening which is intended to be for a spare main halyard (I assume--I've never gone up and checked) but which is currently un-rigged. Historically, I've used a combination of messenger
lines and prayer to avoid either losing my halyard up the mast or a broken
line. After all, it's only Lake Michigan, so worst-case scenario is losing my main 40 miles off shore.
Alternately, there's an opening on the front of the mast at about the right height for the topping lift block but which currently has a plate over it, and I haven't really taken a look at it yet, either.