Hi fit experts--

If I went to a zero offset seatpost, would that mean that I could switch to a longer stem?

I got my current (and longtime) primary bike for free years ago. It came stock with a 20mm offset seatpost. The 57mm frame was always a bit big for me (I'm "all-torso"--5'11, 30" pants inseam), so I run an 80mm stem on it.

In theory, would a zero offset post allow me to run a 90mm stem and still have everything work out? I think a 100mm would be too much of a stretch, as even the 80mm isn't completely ideal. Then again, I run the saddle pretty far back on the post (clamp toward the front of the rails)

thanks in advance