Sorry I didn't see this thread earlier as I have the answer to your question. I have the C3 and a V35 holster which is the same size as the V30, just clip on instead of fixed loop. The C3 fits in the holster, however, it is a tight fit because of the rubber grip ring. I need to slightly twist the C3 just as it is almost out of the holster to get it out. It "may" cause some wear to the rubber ring after some time, I don't know yet because I've only had it for less than two weeks. The switch button sits just slightly above the bottom of the holster. I'm not looking at it right now but IIRC, about .5-.75" above the opening. A Z48 switch "may" be able to be used but I'm not sure because the holster seems to get tighter at the bottom. If anything the switch may bottom out and the light may not be able to go as far down. I would guess that the light could still be retained adequately due to the velcro closure on top.
I am also looking for a holster for my Leef body creation and am wondering if the V40/41/45 holsters are large enough to fit the C3 head through it to the bottom. I was just going to start a thread about that.