I'm a Kilted Roller Derby Referee!!! I have seen a few Kilted Derby fans at bouts and always strike up a conversation with them. Derby Girls love Kilted men, some snickers and snide comments from the fans, as expected.
As to the Question "What does a Derby Ref wear under his Kilt?"
"Kneepads and Skates!" (In truth compression shorts, we get knocked down a bunch)