If shortening a shaft can reduce clubhead speed, it will also reduce swingweight. Can reduced swingweight have any effect on clubhead speed(ie slight increase)?
Shortening a shaft may reduce clubhead speed but generally not by very much. Shortening the shaft both makes the swingweight and total weight of the club lighter. You may swing the lighter club faster but again it may not be much faster. Shortening the shaft also makes the shaft flex stiffer unless you add weight to the clubhead to bring the swingweight back to where it was before you shortened the shaft.