72 year old, in fairly good shape. At times a 4.5 but sometimes a 3.5. Feal l need a little help on serve, good spin but struggle hitting flat hard serves. Good forehand but tend to over hit at times. Tried full bed of poly, synthetic gut mains and poly crosses and full bed of synthetic gut. Little fearful of poly, had tennis elbow years ago. Don't want that again. Realalistly, what would l gain from a full bed of natural gut or a natural gut/poly or poly/natural gut. Using 2 -Yonex 2021 VCore 95 rackets. Thanks, Don