It's entirely possible, yes. Different bows handle different weight arrows differently. Some bows retain energy better and thus put more into a lighter arrow, some do not. Some work excellently with heavier arrows, some lose energy and speed with them due to their individual geometries and draw-force curves. Based upon your input, you have a differential of 56 grains. The normal average of speed loss is 6 grains of arrow weight for every 1 foot of speed, so realistically he should lose around 9.3 fps, not 5fps. BUT, as stated, every bow and setup is different, so 4 feet is not out of the realm of things in any way.If he can use a heavier arrow and gain KE and produce a quieter shot with less vibration thru the system, 5 fps is definately worth it IMO. Good shooting, Pinwheel 12