I had one 219C leftover (more coming..) and because I want them dedomed as well for a build, I went into the slicing business. Never really been there before, I'm a hot dedomer and quite disturbed that my good old method does not work on these.
I had one slightly succesful slicing expereince on a Luxeon Q before, and remembered from that one that I needed a slicing guide. The Nicha dome being so stiff I reckoned that it needs slicing thin slices at a time so here's how I solved that (anyone done that before?):
I have this singfire SS C3 waiting for a build sometime (it is actually too heavy for my taste), with a nice brass pill with flat ledboard base. Sanded that base a bit flatter even, and the flashlight head is a pretty convenient adjustable slicing device. It needs a pretty stiff slicing blade, so I used a spare blade for my little Davids planer. One of those break-blades for utility knives should work as well, as well as a blade for the traditional Stanley knife.
With pill upside down, by slowly screwing the pill out (one 20th turn at a time) the dome could be removed slice by slice, making sure the blade was at about the same angle every time and making long smooth slices with a minimum of pressure. The ledboard was pushed down onto the pill pressing my nail right next to the led. This only works well btw if the led is reflowed nice and flat on the ledboard, or the slicing will not be plane with the die.
I ended just above the die, dangerously close in fact, a fraction of the mm, you can see that at the right side of the die the silicone already crumbled a bit and makes a dip.
It helped for controlling the slicing that it was done under a stereo microscope.
At the right at 0.5mA.
From how that looks, you could sell that :-) . I have not proved the result by making a thrower with it that rivals the latest dedomed XP-G2 S4, but it should work alright I guess, at least the tint seems a nice 4000K to me (but I want to see that of course ;-) )..