Hey, I think that's my old longbow there Rob! Hope you're liking it.
To go one step further, in order for me to shoot a longbow such as the one pictured, HH types, or selfbows, I have to get that thumb joint pictured just to the right on Rob's bottom picture, pretty much in the direct center or just slightly off to the right of the handle.
People are different so don't be afraid to experiment. Also keep safety in mind however.
Much like this (picture from HH Shooters website, picture is not me).