Hi Jerry,
Don't get too carried with the technical information you get on this forum. There are some who speak loudly and don't know what they are talking about. They have never built a boat and never done scientific studies. Never put instruments on a beach cat and taken measurements upon which to base sound conclusions.
The man from Texas is right. If a spinnaker makes a boat dig its bow, the pole is too short. Aluminum tubing comes in 12ft lengths. Therefore many spin poles are 12ft long. It doesn't matter if that is the correct length pole for the boat or not; it is the length that is readily available so that is what is sold/used. A spinnaker that lifts the bows flies from a pole that is 45% to 50% of the mast height. A spinnaker flying in this mechanical arrangement will lift the bow no matter what the bow shape. The flying spinnaker unloads the bow no mtter what the bow shape.
"All boats that fly spinnakers have lee helm". Only boat designs that place the daggerboard in the classical position, approximately at the shroud chainplate, have lee helm with the spinnaker up. This is a system design that has ignored the spinnaker during the design phase of the boat development and the designer/manufacturer expects the sailing public to put up with it. There is a sail/boat design system that does take this CE migration into account. The design system is called "shared lift" and it is incorporated into ARC products. It has to do with shifting the board location forward so that the CE with spin up cannot get in front of the board. Then down sizing the board and up sizing the rudder so that the shared lift between the board and rudder is in the correct effective location for sailing the boat as sloop.
Good Sailing,
Bill