replacine spinnaker halyards

i find 5/16" to be good in the hand and in the clutch.
something low(er) in cost and low stretch like maxibraid.
js

Oh and for length, rules of thumb work fine but I find the absolute best way is to use the old one as a guide.  For example if you find your current halyard is 5 feet too short (as mine is for example!), remove the old one by running a length of cheap polypropylene line taped to the end of the current halyard.  This keeps everything in place and allows for installation of the new one without mast removal or going up in the chair.  Measure the old one exactly, add/remove whatever modifier you have in mind and you're good to go.

For halyard length 78' should do.

They mount to the base of second stanchion at the near widest point of the boat's beam. The spinnaker sheets pass through them and then they are used to help trim the spinnaker. We level them both at about the height of the upper life line for most jibes, and when reaching hard the one through which the guy passes comes all the way down to prevent ripping out the stanchion owing to the angle of the guy from its deck block behind the winch to the forestay which is about where the front of the pole will be. Also in strong downwind conditions we keep them both in a bit to help keep the boat from rolling out from under the spinnaker.

Other things: You mentioned putting tracks back onto the deck for the genoa.......don't. The stance of the shrouds and the length of the spreaders prevent you being able to make good use of cabin top tracks unless you have a very special cut sail, and then I doubt it will work. Also, you said that you thought you were sheeting the clew to the lapper to the track behind the mast.......that's wrong. Both the lapper and jib clew to the deck track forward of the shrouds and mast and, in fact, they clew very close to the front of that track depending on the mast's rake. Next, you indicated clewing the genoa to the rail. Don't. You will destroy the rail if you are hard on the wind. It is meant to be on the deck track right up against the sides of the cabin, just where the deck meets the rise in the cabin sides. From the photos you have that track. The only time you might consider going to the rail with a clew is if you were in a very long close reach and by going outward you keep the bottom part of the leach from curling back into the boat and acting as a brake.

There are many sail trimming articles on the internet. Most of the major sail lofts post very good information on trimming of every sail. However with the foresails you are looking for a balance between foot and leach tension in order to shape the sail correctly for the prevailing conditions. In heavy airs the foot will be a bit more tight which will leave the leach to curve off at the top and dump some power. In medium airs the foot may have a bit more curve in it which will tighten the leach a bit to get maximum power and point for those conditions. In very light airs, you may again trim the sail to twist more. Do some reading. There is lots of it and there is some very good information in there. Try northsails.com and go to trimming guides. Select a boat that has a fractional rig, say a J-105 and read about jib trim.

I also used the Chicago Rigging folks for sheets, they know all the lengths and I bought tapered sheets that have been great, I do sail in a rather light air world here on the Ohio River.    Just another resource!  :)r