On the other hand, if you do get the prop stopped in flight, it's going to be really hard to get it turning again without a starter. I used to fly a J-3 on skis, whose engine had no accelerator pump, and did not idle worth a darn. The result was that sloppy use of the throttle would make it quit, an I would have to dead stick onto the forzen lake (which was my intended landing site anyway). There, I would hand prop it.
I have windmill started my 150, having stopped the prop in flight. It's not easy, you've got to be going really fast.