I am looking for a good ZTR Riding mower, commercial grade that is good on hills and slopes. Nothing extremely steep, but maybe 15 or 20 degree slopes. My 60" Exmark Walk Behind just blew up on me. I have a dixie 50" but it is terrible with hills, as soon as the front wheels turn down, the mower goes down the hill. I live in the Pocono mountains in Pennsylvania so hills are inevitable, and many of my customers have these hills ans steep septics (turkey mounds). Many thanks in advance.