I don't believe my PT would roll down that hill if the engine were to stall. The reason I think this is because I have run the unit out of gas a few times. The engine stopped, and so did the PT. It didn't coast, roll or move. The engine died and the unit stopped instantly. So, if it were to roll, I would suspect it would be slow enough that the pin brake would engage. The next time I am out at our property that has a large hill on it, I will try to see if it rolls with the engine off. Probably won't be until the fall, though.
If it did start rolling, I would wrestle the steering to turn across the hill, and it would stop. I would not fear a tip over on a 20 degree side hill with my PT at low speed.
As for damage to the pump, I suppose if the unit had enough weight and/or momentum to start or keep it rolling after the engine died, damage could occur to the pump. I know PT says not to tow the unit without releasing the tow port or damage will occur. But I think they are talking about more distance than a foot or two. I think they are talking about hooking it up to your pickup truck and towing it out of a field or out of a mud hole. If the tires gain traction their motion could force fluid back into the tank and cause suction on the pump side. Since the pump isn't turning, it might try to force the engine to turn over, suck fluid past the seals, etc.... Someone else with better knowledge of hydraulics should chime in here.
Now if a hose burst, the unit might run away, but the pump would not be damaged because the pressure would be relieved by the hole in the hose. Again, my guess, not fact.
