I have done the drill and or cut an x in .22 and decided that the extra oomph (fragmenting, tumbling etc.) wasn’t worth the loss of consistency.
Never tried the flint in a HP but I have done backwards primers in a 357 HP (that was interesting).
If you really want to push the envelope…. Reload a shotgun shell with split shot sinkers, crimped onto bread twisties or "ring a shell", that’s where you cut a ring all the way around a shell, over the wading, if you cut deep enough, the shot and shell stay together, like a slug, and explode upon impact, kind of like a 12ga glacier round. Another variation is to add a bonding agent to the shot, this is tricky because you don’t want to blow up the gun, but, if you use say a small (read just enough to make the shot sticky) amount of bubble gum mixed with a full load of 7 1/2 shot, you can shoot a fist sized pattern at 70 yards.
WARNING WARNING WARNING if you do anything to alter the design of a round, YOU must take personal responsibility for what ever happens, you just may end up winning a Darwin award!