I can answer part of this(I think).
The forward clew/downhaul (not sure of proper name) line is tied at the forward base of the sail and then (guess) goes through a block on the aft of the snuffer ring then aft through a double block (one facing forward and one aft) then forward to be tied at the aft of the snuffer ring. Is this correct?
You have a mid-pole snuffer for sure. The double-block is part of the mechanism that hauls the tack
(go terminology!) of the sail out to the end of the spinnaker pole, and lets it come back into the snuffer when dousing. This is correct!
Then a rope which is attached to the top of the sail (spi halyard assume) goes up through the ring around the mast, (a ball is figure eight knotted to limit the tightness of the sail) through the pulley on the mast, then back down inside the ring again down through the cleat on the mast you suggest, through the pulley to the right of the mast on the crossbar forward to the double pulley (that the spi downhaul is attached to the other side of) and then back to an enclosed cleat (not sure what proper name is) on the crossbar, then through a hole in the tramp forward through the snuffer bag out through the snuffer ring to the holes in the sail and tied to the top hole. Is this correct?
Yes! Though I am not sure why you need both the mast cleat and the crossbar cleat - the Tiger I sailed on use only the crossbar cleat (a lance cleat
, go terminology again) to hold the spinnaker up; it holds itself in the snuffer just fine
The point to see here is that the same line takes the spinnaker up and down, depending on which way you pull!
So to snuff the spi, you undo the cleat on the mast as you pull the rope that goes though the deck?
Yes - but these are the same line, you are just pulling different directions.
How much slack rope is on the deck or just whatever is left from the 26 meters?
Beacuse the line runs both ways and has no block-and-tackle for mechanical advantage, you don't need much slack at all, and there's never any 'left-over' line sitting on the deck. A mid-pole snuffer has the extra 'double block' that takes the tack out to the end of the pole when raising, but I don't think that adds much in the way of slack to the system.
Dan you mentioned that you only run the halyard to the middle of the tramp as a turnaround. What did you mean by that?
With the one line, the crew needs to pull from fore-to-aft to raise the spi, and aft-to-fore to douse it. Unless your crew wants to stand on the front crossbar, some of the line needs to run aft of the crossbar. The Tiger I have crewed on has the line running all the way to the back of the tramp; I like Dan's idea of only running it halfway - this allows the crew enough room to get a good grip and haul that line like hell to get the sail up and down, without having the disadvantage that the skipper or the mainsheet may get caught up in it while hauling.
I don't own a Tiger, so take my explaination as-is, but I'm pretty sure of this part!