It does slightly overlap with the heatsink that comes with the emitter, but only slightly. This is a non-issue with the flat heat sink, or even just a slightly shortened / tapered heatsink (which would take some doing, but copper is pretty machinable if I remember correctly).
I am curious about the comfort of null's design with the extended sleeve, though I would still have to worry about my hand muffling the sound to some extent.

I'm still mulling over some variations on the perpendicular rod design:
* changing the tip shape
* changing the length
* making them domed nubs (like this but not inset and in brass)

but without any good way to try them out full-strength (I can hot glue wood dowels sanded into shape... it holds kinda well for a while but fails quite suddenly), I can only assume the advice about them sounding "less comfortable" holds true for them as well...