Hey Cookshack,
Another idea. Send everyone with their new smoker a "sizing" device that shows them what an Ounce is (since most people don't have a scale).
It's about 1 1/2 x 1 1/2 x 1 1/2" (about, because the density of the wood will make a difference).
But HEY, this isn't rocket science. The key is NOT to overload it. Just put a piece or two in, see how it flavors and go from there.
And, stop me if you've heard me say this before...
...keep good notes. I'd even dry an outline around your wood so you'll know what size.
Or do what I did and buy a cheap measuring scale that measure ounces.
Smokin'