I'd vote for a big-melon boonie too.
I have to buy the largest Tilley size hat, so if it says "one size fits all", it won't fit me.
I'm more of a wide brim guy. It keeps the sun out of my eyes, the rain off my glasses, and helps make my head look smaller <img src="/images/graemlins/blush.gif" alt="" />
Here is my next one:
Tilley T3 in Olive Ken K.