I don't know and honestly don't care who designed them, they work and from what I've seen are about as idiot proof as can be. So far I have yet to see one that won't run no matter how stupid the owner is.
Now as far as an un-governed puller engine goes your on your own. Just my 2 cents but I'd have a serious blow shield around the flywheel if it was my feet in the explosion area if it was me.