I am trying to model camber in a ~40' piece of concrete and I keep running into problems when I put the last dimension (camber height at centerline).  I can fully define the sketch with larger cambers but when I input the 1/2" camber that I need, it overdefines and calls it invalid geometry.  I suppose I am running up against the size limitation for SW by using such a shallow parabola.

Length of piece is 39' 11.5"

I need parabolic camber of 0.5" in CL.

I also need to lay out 30' 11.5" & 18' 11.5" pieces in the same caber to see how much overall camber they truly have.

See file.