After almost 60 years flying, I haven't seen anybody get hurt being hit by any kind of plane. I once did get hit by a SAM 1/2A Texaco ship in glide, about 14 ounces, gliding at maybe 20 mph. Two of us standing side by side talking got hit by it at the same time. Barely felt it.

Someone setting in the pits at a nearby field was hit by a large scale plane. Almost killed him.

People have been killed by being hit by out of control planes of may sizes. Heck, about the time I went into the USAF in 1964, there was a dissapearance that turned out to be a murder. Wife shot her husband - - with a Daisy pump BB gun. One .17 cal BB from close range into the temple. Something doesn't have to be big and heavy to injure or kill.

Various safety organisations don't even list this sport/hobby in their statistics. Golfing is overall more dangerous. That is generally near the bottom of the list. We usually don't show up on the statistics.

A baseball was mentioned early in this forum. Googled the weight. 5 to 5 1/4 ounces. Interestingly enough, a major league catcher for the local team was being interviewed on a local radio station a couple days ago. Says in spite of the padding on the glove, every pitch HURTS.

Fact is, pitched baseballs, 5 ounces at 60 mph and higher, have broken bones, and even killed people. Once at a fast pitch softball game, I got hit twice in a face protector. I think I was in a state of mild concussion. Mildly sick, dizzy, and a major 2 day headache. I was amazed when I read an article in one of the health and safety mags I get as one of my side jobs with my company. It seems as many as 12 kids, catchers, in little league, hot stove, and high school and even college baseball are killed every year, in spite of chest protectors, by having their hearts stopped by getting hit above the sternum.

Seeing as how most flyers have enough brains not to hit someone, or even fly close to others, but accidents (and sometimes stupidity) happens, I'd vote for something a little more conservative, like maybe 18 ounces and 40-45 mph for the park flier definition.