Kind of a weird thread.
1) Different face masks/helmets are used to reduce likelihood of concussions. I think the players have said who cares on style and they want to protect their melons as much as possible.
2) Distance. Who wants to travel to the VMAC to get smacked in the mouth? I bet with the joint practices, one common denominator you'll see is that the teams train close. And as an aside, the Hawks really don't have any trouble mixing it up with themselves. I'm guessing a joint practice would provide PCJS a headache that they don't need. When your own players are throwing punches at each other without helmets on, you're going to try and keep it civil as much as you can. Adding another team to the mix probably wouldn't help.
