When Runcam released the Runcam Micro Swift only a couple of weeks after the Runcam Mini, I wanted one. I had just bought a mini and thought they looked about the same, so I printed a new case/lens holder. Since then, I have made adjustments to make it fit/look better and these are the product. All work, V3 is simplest and fits well without being too weak or too big for what I wanted. V2 is a bit closer to the actual runcam micro shell size but my first one had some light leakage after flying for a while. V1 also works fine, but I decided to slim it down a bit. It requires a lens from a mini or full sized runcam...or from a runcam eagle. I haven't designed one to use a micro-sized lens.
I would have posted sooner, but I moved to China for a couple years and didn't have much chance to fly or print while there. Now that I'm back I'm getting back into printing and flying all over again and wanted to post this in case others may find a use.
Printed in PLA or PETG...both materials have worked great for me. Slower is better to get the threads printed properly (even then, its tough but can be fixed). Also, it prints fine with 0.4mm nozzle, but recently I printed a couple with a 0.3mm nozzle and like the results. The one with the micro VTX attached in the photo was printed with 0.5mm nozzle, so take your pick. I printed with supports as shown in the photo above.
Since the threads are so small, they may not print well, depending on your printer and print speed. If it doesn't thread well, it helps to heat it up, just a bit, before screwing the lens in for the first time. It works well if you partially thread the lens and then warm only the lens using a heat gun. Don't go crazy with the heat or the base will warp and won't fit properly anymore. Attaching the camera sensor also helps keep the body from warping out of shape. Once the lens is threaded all the way in for the first time it should not give you problems anymore. For my cameras, the lens needed to be threaded a little less than halfway in to get a clear picture (should be about the same as with the stock case.