I'm using the 57mm Fiddle Ratchet Block — Swivel, Becket, Cam Cleat Product No. 2676. Get the spring that holds it up when it's not in tension.
Again, if it were me, I'd taper the battens. Meaning I'd buy the Hobie 18 Luff Cap Kit (Trentec). You get more than you need but hey ... I'd replace the second batten down with a full width batten, then you'll need the larger leach cap. and then taper them all so they have the draft at 40% to 50% of chord, all have about the same tension, and are all the correct length (batten cap just touches the sail when tensioned). My battens, from top to bottom, are 5 lbs, 4 lbs, and then 3.5 lbs. for the rest. The sail gives them shape but you just want to help it along.
Oh and a tiller extension. My favourite is a carbon golf club (Value Village or Angelview, about $5) with the head cut off and the Omniflex Tiller Joint Universal epoxied on the end. Also the saddle thing that adapts the flat base to the round tiller connector tube. I think it's the 32 mm one.
The list keeps on growing. When you lace the trampoline do it with 1/8" or 3/16" line. Then redo it. When you get the second lacing tight the first one will be loose. Tighten it up. Let the whole deal sit in the sun for a few days, then repeat. "Tight tramps make fast boats."
About 5 feet of line for your 3:1 downhaul. All I can think of right now.
Have fun, and have a Hobie Day!