Profile view scaling

I have been making plots of fault slip models with GMT for many years and it works great. I typically make both map views and side “profile” views. I have been using the classic psxyz to do the side views. My fault slip model is a set of polygons with XYZ coordinates of the corners, but the X and Y are presently in longitude and latitude degrees and the Z is in km. I was trying to figure out what projection parameters I should use to get the horizontal scale the same as the vertical scale. Is this any easier when using plot3d in modern mode? Below is an example of one of my plots.