I have the 48x 34 inch kohler shower with built in seat and was looking for info about the fit of shower?

Walls do the shower walls fit the shower seated unit and can I cut them so the window will work or will chipping happen or will side walls work and also use tile for the back what do you suggest|||If you cut it it will lose it's integrity and there will be a weak spot. Plus it will have to be resealed against water leakage.