A lot of people use a rear finish mower and a rotary cutter on the small tractors. Manafactures have gotten scared of the litigation crowd and are placing as many barriers between them and the Court House as possible.
Did you try engaging the pto,setting the parking brake and dismounting the machine,on my gc2300 i was able to do that and the pto &tractor stayed running,give it a shot and report back.
I tried setting the parking brake first, then engaging the pto. When I got off the seat, it quit. I'll try engaging the pto first, then setting the parking brake and see what happens.