Gray,
It's good to hear that you find your mechanical thumb effective and useful. I was hoping somebody who owns one would jump in. Like I said earlier, I like the idea that it's simple and relatively inexpensive, it weighs a lot less, and it's
one less operation to deal when manipulating the hoe. Another consideration is that fact that the L39s have internal hoe hydraulics. It might take some time to safely plumb hydro pipes on the exterior of the boom and dipper stick.