- depends on shot
- i like to hit winners hard, 100%, when i'm set up properly because it's fun!
- most rally balls and approach shots i play for position, so 80-90%, otherwise you'll lose against consistent guys
- in every long rally i will hit at least one hard 100% shot just to mix things up and intimidate opponent
- i don't see the point of hitting less than 75%, might as well slice, drop shot, moonball, come in for volley/half-volley or choose another tactic
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM