I was playing the other day and serving normally, the pace of my serve usually hits close to the line and bounce and reach the back fence. By the third set I was getting tired and double faulting. So I took off a LOT of pace , by justing serving with arm motion and not letting my feet leave the ground or have any forward momentum. Essentially I was pushing my serves and letting gravity fall the ball in the middle of the service court and barely bouncing it to the back line, no where close to my normal pace. This seem to work really well. My opponent usually feeds of the pace of my serve , This time he trouble and hit some returns into the net. Now I thinking this might be a way to conserve energy and throw some unexpected change ups serves. So I serve mostly weak slices, reverse slices, I even thought about underhanded serving To mix it up, I served a few fast pace serves. He couldnt hit a winner of the returns plus made a lot of unforced error into the net. I never seen anyone do this. Legit strategy?