Wow, some people sure can get mixed up by trying to picture rigging when you type about it!

What David L. said is right.

On my Nacra 6.0, from the spin clew I use a ratchamatic off the shroud tang. Then the line goes forward, allowing a contant nearly 180 degree turn, then thru a block that was the bottom block of a prindle 16 mainsheet system. (sorry, no part number).
This block has the switch to turn on or off the ratchet, so in light air, it freewheels, and when needed, it has alot of drag being only unidirectional with the ratchet on. This really takes alot of the loads off the sheet, and still allows for good spin control. Face it, especially in a distance race, you pretty much leave the spin sheeted to it's sweet spot for the course and conditions, and control things with the tiller, and alittle main traveler-at least I do anyway.
ON my 6.0, to get the spin sheet out of the spaghetti bowl of sheets with the 4-way jib system, I then route it thru a third block on each side, just a turning block, to get the spin sheet back behind the 4-way jib lines. With a smaller chute, (ideal for these boats-sorry Randy), the two block system is needed anyway to get the sheet around the daggerboards, then I use a third to get it back behind the jib sheets.

After tailking to many I-20 sailors, and Tornado sailers, such as J. Tomko, and C. Ogletree, their advice was to have either two blocks that you could turn the ratchet on/off, or one and a ratchamatic.

The doubler is another good idea, and I've used that set-up in the past, but with my current set-up, it's not needed. When I get around to it (ever say that?), I'll also put a cleat on the windward side for the spin sheet in distance races.

To make a long story short, get a ratchet for the second block, with a switch to turn on or off when needed.

It helps to snuff, when the ratchet freewheels, so there isn't much tension on the spin sheets while going in.

My 50 cents.

Todd Bouton
Nacra 6.0na
#111
with I-20 chute, and mid pole snuffer, square top main, ...