shower base installation

Hello! I am installing a mustee shower base (32x48) onto a concrete floor. The drain pipe is sticking straight out of the concrete. The problem is that the bottom of the base is not flat. It has about a 4" deep protrusion where the pipe goes in the center of the base. The instructions say that if installing onto a wood floor that I must cut a 5" hole to accomodate this protrusion. Should I chisel out the concrete aroiund the pipe or would I be better off just getting a different base?

You will need to break out some concrete.
It's the same with any pan.