Tapering the fletch end will affect spine by 1-2# on the tester-insignificant. Footing won't make a small change..........you are removing 50 gns of cedar and replacing it with 100 gns of hardwood so a 50 gn change spread over several inches. I once made up some Doug Fir arrows with an 8" cocobolo foot-the foot is actually 14" including the splice, spine remained unchanged on the tester, and it increased the weight of the shaft by about 100 gns; but spread over a longer area-effectively about 10#of spine.