>> Even though a girl's bike would lead to fewer scrotal injuries. <<

Very astute point. I have to admit one of the nice things about having a female body is no long having that vulnerability -- and being able to ride a girl bike without anyone staring.

>> As a kid one of my 'tricks' was swinging to side saddle on my 'boy' bike. <<

I've done that. I was far more inclined to ride without using the handlebars though. It always reminded me of flying, to be able to turn the bike without using my hands, only shifting my weight to bank.