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RX100 works surprisingly well for IR, about on par with the Fuji X100 in fact, only while the X100 would allow you to shoot handheld at iso 3200, the RX100 doesn't look so good at such a high ISO, so its more limited to using some support and low ISO, but it does give a rather nice file.
Make sure you've got the red ring part on your new filter holder as well. Its got the little inner bevel that basically centers the filter onto the thin attachment strip on the camera.
I've got a great little L bracket I made for it as well, that I need to finish up and post some images of. I found that I could just bevel the edges into dovetail with a dremel, and than rather than use a fullsize arca swiss clamp, one of the mini hotshoe clamps from my speedlights works.
Its basically a scaled down acra swiss system that cost about $15 in parts, works great, and honestly is a more useful size for such a small camera.
Then even cooler, is using another one of those little hotshoe clamps, I attached a little 2" riser bar and flat plate with a thread for a mechanical shutter release. Using the lock on that, I can set the RX100 to bulb mode and do long exposures.