Think you are a dab hand with a mallet... share it here
Here is how some others do it...
http://www.hardcourtbikepolo.com/?page_id=6
http://www.youtube.com/watch?v=ylBl9qFsFLg&eurl=http%3A%2F%2Fvideo.googl...
Whatever you do, do not use PVC for your mallet heads. It shatters! Use ABS or HDPE (High density polyethelene) or MDPE (Medium density polyethelene).
Ski poles are the preferred shaft. However, some people like golf clubs, canes, crutches, other metal pipe, etc.
Whatever you do, find what works for you!
A few people in East Van have fully operational set-ups for making mallets. Contact James, Rawbie or L'Il Miss Used if you are interested in making a mallet.