Sam, Bowstrings have changed quite a bit over the past twenty years. For many years Dacron was THE string material and it is still the easiest on the bow in terms of transmitted shock when the string returns to brace height because it has considerably more stretch or elasticity than the more recently developed high performance materials like Dyneema, or fast flight. This is the string material that you should use for older bows for several reasons-all structural. Newer bows are usually fast flight compatible and are constructed to withstand the shock generated by the sudden stopping of the string at the completion of the shot. All but one of my bows are over thity-five years old and I use dacron on all of them but I don't think anyone would argue the improved performance of the newer materials even though some shooters prefer dacron on the fast flight compatible bows for subtle reasons of their own. If you use dacron, you should be okay with twelve strands up to forty-five or fifty pounds and add two strands per every ten pounds of bow weight beyond that. I prefer lighter strings and use only 12-13 strands of dacron in my 65-70 lb. recurves but I make my own, check them carefully, and change them often. I am not advising it for anyone and better safe than sorry- broken strings are not fun with any weight bow. The various modern materials come with different recommendations and can usually be purchased at safe strand counts by designated weights. Good luck, I hope you enjoy this for as many years as I have,
Grant