Hi John,
I just returned from sailing in the Tradewinds Regatta in thr Florida Keys. I saw many different types of boats with spinnakers. Most boats have poles that are too short. When the spinnaker fills, the bows dig and the skipper and crew head for the back of the boat. I think that the reason for the short pole is that the longer pole pushes the CE further forward and requires even more mast rake than we see today to get rid of lee helm with spinnaker. Now take the spinnaker down and the sloop rig CE is so far aft that it stalls the rudders. So what do you do??? Go with a short pole and small spinnaker and less mast rake and live with it. You can "get by".
A better solution is go with the long spinnaker pole that lifts the bows and move the centerboard trunk forward a couple of feet to trim the boat out with spinnaker. Now without spinnaker, this will automatically reduce the side load on the forward located centerboard and increase the side load on the rudder. Therefore downsize the centerboard until it is carrying the boat's original design point lift per square foot of board area and upsize the rudder until it is carrying the boat's original design point lift per square foot of rudder area. This puts the centerboard and rudder back to operating at their respective design point loadings which results in the these foils operating at their highest level of lift to drag ratio while the boat is sailing to windward.
The other scheme of raking the mast back and balancing the rudders and "live with it" is a second level of performance compromise, a slower boat to windward.
Bill