Spent many years working SLOOOOOW pitch. I never wore a mask but at the time I was a little faster than the average bear. There were many close calls on foul balls but I was almost always able to either move my head or get a hand up.
It is not the speed of the pitch that will get you like in fastpitch or baseball - it's that last second redirection and the incredible spin put on the ball when the bat just slightly nicks the ball. Threads and that spin could very well chew your face up.
I've seen a few catchers use a mask... Some may scoff, some may jest, life with safety is still the best. They may have gotten heckled but they still had all their teeth.
I guess if I was still regularly working slowpitch I might look into a very lightweight mask. I still have my teeth also but I am getting a little older... and perhaps wiser... surely more humble and less reckless.
Check out the gameface for $30. It is actually made for players but would also work well for a slow pitch ump.
http://www.gameface.com/
[Edited by DownTownTonyBrown on May 4th, 2004 at 10:09 AM]