actually.. 3u or 4u depends on ur hand and wrist power.. i have slim and skinny hand.. but i insist on 3u racket whether i play single or double.. 4u feels too light and not comfy.. feels hollow too sometime.. shaft stiffness too plays an important role.. it really boils down to personal preference.. u need to just go out and try out ur frens racket.. swing with empty racket for me dont provide accurate feel about the racket after strung.