All good stuff.
I try to use a bladed stance (strong side forward) regardless of what kind of cutting I'm doing. On downward blows, I can flex my leading knee a bit, dropping some of my body weight behind the swing. Besides giving me some more power without a loss of control, it changes the dynamics of the work drastically: the potential energy of the raised khukuri and my body do the chopping, and my knee (rather than my arm) does most of the work in replenishing this energy from swing to swing.
I try to keep my swings well clear of my body. Assuming that my right side is forward and my stance is fairly bladed, a swing from right to left is almost impossible to hit myself with. Coming back from left to right, the swing is backhanded and is probably the safest swing one can make. I used to keep my free hand behind me for balance but managed to hit it once like that (I have no idea how) so these days, I keep it against my chest.
The most important thing, safety wise, is to swing in such a way that the khukuri cannot come back at you, either from overpenetrating the target or taking a bad bounce. (I've caught a bounce and while it healed well, it left a mark on me both figuratively and literally.) The terrain that you're on, the angle and condition of the wood, and the amount of force that you're using all play a part in the best way to cut.
In general, force is inversely proportional to control. If it's a tough angle, use an absolute minimum of force or figure out another way to approach it. Hard swings from tough angles with body parts in the vicinity are a recipe for disaster.
Also, make sure that no one is nearby. Getting hit in the face by someone else's woodchips is annoying; getting hit in the face by an errant khukuri is far worse.