Just above the forestay is probably better
You're probably better off positioning the block so that the head of the chute is at the same height (more or less) as the head of your jib. That would be consistent with the rig design. If your mast is like mine, the upper shrouds and forestay all connect to the mast at about the same height so that the shrouds (which are angled backward) can oppose the forward pull from the forestay. Placing the head of the chute at the top of the mast means the only thing opposing the forward pull on the mast would be the bending resistance (stiffness) of the upper portion of the mast. If memory serves me correctly, the H23.5 has no backstay. These mast extrusions are not very stiff and they bend very easily when unstayed, so you may be loading the mast in a way that probably was not intended. My Z-Spar mast is a fractional rig like the H23.5. It has two halyard exits, one just below the forestay (for the headsail) and the other just above (with a special horizontal flare) for the spinnaker. What's odd is that there's no mast exit or cleat for a spinnaker halyard at the mast base. Provisions were made to add them, however... Peter H23 "Raven"
