Hi Don,
I have a Coronet 20 in pretty good order. It's down at the marina but I will look at the rigging when I'm down there. The topping lift for the spinnaker pole is shackled on the inner fore stay (jackstay)connection. It's actually on the same fitting which attaches the jack stay to the mast which is riveted to the mast about 100mm above the spreaders. Not at the top of the mast as you suggest. You could have it away up there but there is no need. The down haul is thru a block adjacent to the base of the mast. My boat no longer has a sliding gooseneck for the boom fitting but I get enough tension on the mainsail luff with the (spectracord) halyard.
As far as the centre board goes, I hope not to have to re fit that. I think the stainless steel cable is about 1850mm long and about 4mm dia. Just pull the system apart and re build it, including the sheave on the top of the centre plate. Probably should replace the king bolt which pivots it through the lead keel. Sounds like a mission although once you have the boat chocked up high and the centre plate down it should be easy to work on.
I have removed the wood trim around the gunwhale and glassed over it as the screws and rivets were leaking water into the boat. Also the main sheet traveller was leaking through the bolt holes which hold it down to the seats in the cockpit. I removed that and re sealed it.
The trailer is a Reid Trailer and a pretty good design for the boat with a lot of central rollers for the lead keel, an extention for launching and a tilt for retrieving. Single axle. Because the boat sits up high on its keel on the trailer, you have to fully immerse the trailer wheels to float her off.
They are great boats, very seaworthy. We were out yesterday in the harbour in pretty strong winds and she went well.
If you want I will send photos. Will take me a few days before I get them.
Cheers,Grant Timlin