I have a symmetrical on mine and, to be honest, the rigging is a work in progress. The method recommended by hunter for the 23.5 is shown on a diagram in the owners manual. You can find a copy of the manual in this thread if you don't have one.
http://forums.hunter.sailboatowners.com/showthread.php?t=141541
I basically have used this configuration. My spinnaker uses 1 guy, 1sheet. I don't have tweakers attached. For the downhaul, I just attached it to the base of the mast as the diagram from hunter uses a block attached at the mast base. This isn't really ideal. It would work better if the downhaul attached further toward the bow, but there is no good place for attachment that I've found. There's a discussion here that has some suggestions I might try this year.
http://www.ybw.com/forums/showthread.php?t=263843
See the post by williamH. The idea of using tweakers without a downhaul might work well. Just still a problem of finding attachment points far enough forward for this to work. His idea of individual downhauls on each side might work if the blocks could be attached at the stantions on either side near the bow.
More info and pics on spinnaker setup below:
http://www.harken.com/rigtips/spinnaker.php
http://www.hmc.edu/org/sailing/sailing-spinnaker.htm
I still also have to rig up a couple of turning blocks somewhere near the stern of my boat. Currently I just fly the thing like a kite without the use of turning blocks. Not ideal, but I only use it downwind in light air.
Hope some of this is helpful. Do post some pics of your setup if you get something that really works well.
