I'm a large guy and use the Honig's K2-Fastpitch Elite protector. It took a couple of games to get used to it. Can't say if it would provide you enough protection or not.
http://www.honigs.com/detail.asp?Cat=2&Sub=58&Item=363
Know several people who use the Ump and love it.
http://www.honigs.com/detail.asp?Cat=2&Sub=58&Item=605
I personally don't like the hard-shell protectors...they look too bulky.