Help with field height with board with legs

[tbuc]

Can anyone tell me when you are putting folding table legs on your board what should be the final height from the floor to field level. I ask because many people like to sit down while playing and I do not want to make it uncomfortable for them. On the other hand I do not want it to be so low that you break your back bending over to play? Is there a happy medium or how do you determine your field height.

Thanks
Mark