Typically, I move the drain to the center of the shower...if for no other reason than aesthetics, it allows you to mud the floor pretty much equally. If it's too close to the shower head, the slope from there to the closest wall is considerably steeper than other areas...

You may also want to think about where you will most likely stand. Do you want to stand right on top of the drain? (Usually not the most comfortable). If as ST said, the slope is too steep from the front to the drain, would you find that comfortable to stand on?

StoneTech and raehelen, thank you very much for your help.

Yes, the contractor suggested the shower drain at the front because it's not comfortable standing on the drain if it's in the middle. I'll bring the issue of being too steep from the front to the drain to my contractor.

Or you could do a linear drain at one of the short ends. That would give you a more gentle slope. There probably already is a drain hole where your tub used to drain, so you wouldn't need to move it.

-Babka

Really a matter of taste, here. I still like em' centered. Unless you only have one leg, you generally aren't going to be standing on the drain. I usually straddle the drain naturally when standing in the center of the shower.