I’m assuming that your trimming the shaft an additional 3/4″ than the original shaft?
increasing the weight of the shaft by 10 grams will cause approximately an increase of 1 swingweight, trimming the shaft by 3/4″ will decrease the swing weight by 4-5 points. Few other variables are involved also.
Going with the heavier shaft will give the club quite a different feel. What are your concerns in trying to trim it to a certain swing weight?