I have a walk behind self-propelled z-turn Honda lawnmower. It has the feature of locking the front swivel wheels in place for holding hills, etc. One particular place that I mow has a 75-80 degree hill that is mowed. It is too long of a hill to go up and down. Can I change the wheel size or change the tires to rubber or what do you all recomend to solve the problem of my lawn-mower wanting to slide down as I go across the hill? I have also thought that more weight on the machine would help. I know that it weighs more than most because it is a commercial bagger. What do you all recommend?