Mike,
How many posts do you have that you want to cap?
If you don't have too many to do, why not just take a circular saw, or if they're out in the field and you don't have a generator in your FEL, a chainsaw, and just cut an angle at the top of the post? A simple 45 degree cut would be sufficient to let the water run off.
Just an idea. /forums/images/graemlins/smile.gif