It depends on how your sail is cut. I had a #4 built for ocean racing that comes all the way to the deck like the #3 so the sheeting angle would be forward of where you sheet the #3 in to. If you have a high clew on your #4 then you will want to trim it with the car back further.

The best way to tell is to hoist the sail and tie a piece of line to the clew. It should be approximately a 45 degree angle to where the car will be. In other words, a continuous imaginary line should go from the midpoint of your headstay, through the clew and to the car. That will at least give you a rough idea of where the track should be.

IMHO, you can get away with a 24" (or maybe even 18") track up front to cover the #3 & #4. Then you will need about a 36" track back aft to cover the #1 & #2. Of course this is going to mean you need two cars on each side to make it work.

We have the ocean lewmar adjustable tracks on Moxie and have one continuous track. Not sure of the exact length but it is at least 10-12 feet. I would call around to a bunch of different places and see if you can get a full length track. Then you only need one car and don't have to worry about sheeting angles.

-Jason

:: I am going to upgrade to adjustable genoa leads. I
:: boujght the Lewmar ocean size 0 system (because it was
:: way cheaper than the harken) but the track only comes in
:: 7 ft lengths. The stock T track is around 8ft. I
:: orginally wanted to have a single curved track so I was
:: sure to be able to trim all my old sails. I have a #1,
:: #2, class jib, and a #4. Since it is looking as though I
:: am going to have to go to a split track on each side I
:: need to know where the #4 trims to? I have only used the
:: sail a few times and can;t remember how far back I moved
:: the lead from the #3 position. Any one have any idea?