I'll give them a short tour to the nearest lot and tell them how to get to Walmart for a $20.00 lid.
Even though the pd would have a difficult time enforcing the rule, one can suggest to those without helmets with a little more to back up the suggestion.
Last week Wednesday and Thursday, 3 late teen/ early 20s riders were out without helmets. I had mentioned it to them every time I went past them. On Thursday, they were on the launch hill of the table top and I mentioned it again. Then demonstrated why
Did an unexpected one footer, landed it, avoided two trees and slid down at the base of the final hill. I heard them say "We believe". Just a flesh wound. (shin skin)