I have some questions i'm sure someone out there can answer. I shoot a Morrison longbow (49#) with 250 grain heads on a 27 inch arrow which are spined correctly. I want to up my poundage to 54# and I was wondering if you thnk the spine will change from these 5 pounds. One guy I asked said I might have to lighten my point weight and if this is true how many grains do you think i'll have to drop as a rough estimate.The reason I ask is I have 100 grain inserts in my arrows and i'm using 150 grain heads and there aren't many options out there until you get down to 125 grains. Thanks for the help.

Since your morrison is cut to center or maybe even past center I doubt that 5# difference in weight will matter at all. If it does just put something behind your strike plate to move it out a 1/16" or so.
Bob

30 grains lighter or so should get you there. Try the 125's and see.