As a closing note, on the topic of shaped charges: A shaped charge is simply a given quantity of explosives which is designed to deliver a greater amount of energy is a certain direction, rather than an evenly distributed impulse from the explosion.
Now I'm no expert on shaped charges but I'm sure the purpose of them is to concentrate the blast at a particular point, therefore rather than blasting the target to pieces, it simply punches a whole through it. Unless the charge simply can't get through the metal the panel would stay in place, just have a hole in it, and not large enough to climb through. There is also something of a backlash.
So for X equivalent tons of TNT, a shaped charge will have a lopsided distribution of explosive force in one direction or another, rather than an even spread when compared to said equivalent tons of TNT (or whatever explosive measurement is used in Star Wars). This means that the minimum safe distance on one side of the explosion is somewhat reduced, but there is still the danger of shrapnel from the explosion. In order to be safe, the HKs might have to get "over the horizon" on the hull or risk being struck with high velocity fragments.
Lastly, there is little research on how well explosions propagate in space. One possibility is that without anything to absorb the force of the explosion, the blast radius may very well be increased when presented with empty space. This leaves the risk that the HKs could be blasted off of the hull if they are too close to the center of the blast.