You may have to do a trial and error set up with sheaves and ropes in order to find the perfect placement for your tracks and cars on the combings. This is what I had to do on my O'Day 222 back in 1986 when I bought it new. The tracks/cars and winches were supposed to be on the cabin on my boat and I had them left off at the factory when the boat was being built. I didn't have a furler back then, but luckily my tracks seem to accommodate my CDI Furler today. At the time, I figured that the car should be placed so that the sheet coming from it to the clew of the Gennie would intersect the center of the luff of the sail, if you drew an imaginary line from the clew to the luff. In other words, this imaginary line would divide the sail in half at the luff. So, if you were to reef your Gennie, you would need to move your car forward to get the same sail configuration by either the placement of the track, or a longer track. I took my boat out on a light air day and did some trial and error placement of the sheet and was able to come up with a perfect placement of my tracks and winches. One other thing that I did that I shall never regret doing, was to place an open clam cleat directly behind each of my Gennie winches for snubbing my sheets. I recommend this highly to anyone who likes to single hand a sailboat regardless of size. Please disregard that small cheek block behind the black clam cleat in the picture. This cheek block was part of a self steering modification that I had installed on my boat years ago that didn't quite work out. I removed both of these small cheek block last fall and plan on filling the bolt holes this coming spring.
Joe