Don:
The way I have seen this added is by through bolting into the mast head cap. There is room for this but you will need to drill and bolt on a mounting bracket or bar. The other way is to re-run your mast head halyard so that they main halyard and the jib halyard align fore and aft. This open up the second slot where you can now run ONE new halyard from Front to back over these two sheaves that line up. You see there are 2 sheaves aft and 4 sheaves forward. The two aft line up with the two middle forwards leaving two outsides open. This can be used but you will need to run that line internal and then out the front outside sheave. When these boats are rigged, sometimes the green main halyard is in the aft starboard sheave and the red jub halyard is in the port forward sheave. This means that there is no front to back sheave slot open.
So, what I did was to move the green main halyard to starboard and move the red jib halyard to starboard. This now opens up ONE SLOT front to back outside and over everything. This new halyard now can be used as:
1. Spare Main
2. Spare Jib
3. Spinnaker
4. Safety line when going aloft
5. Climbing line going aloft.
This idea is in my opinion, the best way to rig the halyards and an easy way to get a spar or a spinnaker halyard without adding one thing. Just re-rig the halyard like this. Maybe there would be some chaffing with a spinnaker since it is not at the top, but for spares this works great.
Here is a photo of my mast head:
Here is exactly what I am talking about. Red and Green to starboard lining up. This opens up the port for a halyard to run front to back. This is your spare and your spinnaker...
Has anyone else done this????
Hayden