I am looking for some feedback on the functionality of an under snap action thumbhole lever. I have my eye on a Boss hammergun with this setup and not familiar with it at all. Is it reliable or problem prone or something else? How does it measure up to a Jones underlever or sidelever? There has to be a reason that this design was discontinued years ago or is it simply evolution. I hate to invest any money into a nice gun if I'll be disappointed with the breech opening mechanism...thanks again for your comments.