it definitely can make a difference, depending on whether your riser is cut not quite to center, just to center, or past center. I shoot a Sheepeater Spirit (very short 50" static recurve) that was being kind of critical of the GT 3555's I was shooting with it. at 51#, I knew it was right at the dividing line between one spine and the next.
I was changing point weights, nocking point, and was about to start cutting the shafts down to stiffen them up, when a friend suggested sticking a little bit thicker piece of leather on my existing strike plate, thereby building it out some. lo and behold, that's all it took to dial in like a laser. of course, with longbows mostly not being cut to center, it can be more of a problem than with most recurves, but it's definitely not something to overlook, particularly if you've tried other remedies without success.
good luck!