5dracing,
I measured the inside of the bar end (can't remember the exact size at the moment) then used the closest drill bit for the 6"x6" block of wood. I cast a small piece of wire in a hoop shape into the weight end for future removal. A small amount of silicone holds the weight in place.
As far as adding weight to the bike, I figured I'd never notice a few ounces on a KX500.
Initially to test the bar weight theory, I placed a weight in only one bar end. After riding a while, I did find the side with the weight viberated noticably less.
Timbowe is right about the breathing thing as well. I try to breath the same way and it works great when I actually remember to do it!