Hi, Vic (had to double-check your email address to check that name wasn’t a wind-up!).
The hook you need to modify is the grappling hook, in-fact I’d go so far as saying the Cliffhanger hook is pretty much redundant these days (it is light, so it still has its place). I usually carry two pointed Grappling hooks (don’t make them sharp, just narrow at the tip), one cut down shortened grappling hook (good for flat edges), a Flat Moses Logan hook and 2 pointed Leepers. I also always have a spare of each hook in my haul bag, as dropping a hook is easy, but climbing with just one isn’t (well unless you’re Steve Mcclure!).
As for climbing over overhangs, the trick is to use adjustable daisy chains (Yates or Fish ones are much better than Metolius or Petzl ones), as you gain a mechanical advantage, and can just crank yourself up. Otherwise, you end up swinging around trying to lock off with one hand, while the other tries to get your fifi hook into a daisy pocket.
Another tip would be not to make the beginners mistake of making your cord between your fifi and harness too short (see chapter and diagrams in Hook book), as too short a connection can make it much harder to hook into a daisy. Secondly being greedy, and trying to get the fifi into the highest pocket (fighting your body and gravity to do so), can take a huge amount of energy (the trick to big walling is to save it), and often going one pocket down is easy. As you can imagine an adjustable reduces the need for fifi hooks. But I guess climbing roofs is always harder work (and scarier) due to you not being able to touch the wall, and so swing about… and because you’re pulling directly down on all your gear : (
Hope that helps, and thanks for buying Hooks book.