I've recently developed tennis elbow. I had it many years ago when I had a light stiff racquet so I'm surprised to be getting it now with my heavier racquet. Part of the problem is I hit my backhand harder nowadays with a few mishits. I'm currently using an old racquet which hasn't been restrung for several years. Could this be part of the problem? It is multifilament which should be arm friendly. My other guess is poor technique on my backhand.