So there are tons of methods to shooting a handgun. And lots of debate about what to do with your support hand. Isosceles, Weaver, cup and saucer, grabbing your wrist, thumbs high, thumbs forward etc. The list goes on and on. However this is a first. If you subscribe to the c-clamp/thumb over bore AR style of support hand grip, then I suppose there could be justification for putting your support thumb on top of the slide. But I don’t think putting your thumb on top of the slide is a good idea. A whole new meaning to slide bite.