i played a guy who had 30 on volley speed and stamina
everything else was 90-100 and he was all the time returning near the service line. i mixed it up with fast serves slow serves, kick serves slice serves and all i could do was to hold my serve once after 5 deuces of boredom.
there is no rule in itst that u cant use it, and even 40-90 wouldnt solve this problem, cos the returns come back before the service animation is over and even if i make a slow serve, then i just about can stumble to hit the weak shot back. serving hard against this kind of return is totally useless, cos then my feet would be still in the air and the return would be already past me.
so what do you guys think