This is from Matt Miller
Locking the Hobie 17/18/20/21 Halyard:
It is best to simulate the halyard locking with the mast down so you clearly understand the system. Then, depending on how old the boat is, be sure the hook does not have the old "flopper" stainless piece hanging on the hook. This old device caused difficulty in raising and hooking but would make it easier to release and lower. Also, be sure that the knot tied to the ring is very low profile. A long bowline knot will hit the mast head before the ring gets to the hook. If the ring has a small loop at the top... The line should be passed through the loop and a small knot tied. The knot (when ring and shackle are afixed to the sail) should be facing the mast. This tilts the ring closer to the mast. Then (before attaching halyard shackle to the sail) spin the haylard 3 or 4 times clockwise (looking down on the shackle). This "pre-loads" the halyard line and causes the ring to swing back towards the hook. Keep the boat into the wind and hoist. Should lock easily. To release... fully release the downhaul and outhaul. Partially feed the sail up the luff track. Hoist with the halyard to the top till it stops, hold... rotate the aft of the mast base to starboard, hold the mast rotated, ease the halyard a few feet before releasing the mast. Lower the sail.
The ring rests, or all of its downward pressure, is on the hook itself. I don't understand the reference to the groove? If the groove is the luff track the ring need not be in the track. Unless you are getting some forward pre-bend by having "your rake too far forward" (which is virtually impossible) rake is not the cause. I like Matt's suggestion of laying the boat down on it's side (it's very difficult, for me at least, to see exactly what's going on at the top of the mast from 30 feet away).