Hi Doug, really great questions! I've actually never tried the in-camera focus stacking/focus bracketing as Sony cameras don't have this functionality as far as I'm aware. The Laowa lens is also completely manual so the focus can't be controlled by the camera. One option would be to change the focus manually and while you could create some contraption to do this automatically (i.e. a rubber belt around the focus ring connected to a motor), it seems like a less precise method than just changing the distance. I imagine you would also need to reconfigure it for different lenses that have a different focus throw (change in focus for a given rotation of the focus ring). If you have the functionality in the camera, it would definitely be a lot easier than manual focus stacking. I'm not sure if there are any downsides, the folks on photomacrography.net would probably know. I wonder if it might have trouble for really "deep" stacks (in terms of distance covered and not necessarily number of photos), since the size of the subject on the sensor would be changing as the focus/magnification also changes. But I don't imagine that would be an issue for most coins at around ~1x magnification. I'm guessing your extension tubes maintain electrical contact between lens and camera so you would still be able to use the in-camera focus bracketing with them? The Laowa is a really nice lens but probably not worth upgrading to if you already have the Canon 100mm and the extension tubes are working for you. Yeah I find it spins too fast as well. There is a setting to adjust it but I couldn't quite find the right balance as when I started slowing it down it appeared to get quite choppy. The setting also has no units (e.g. frames per second) so it's hard to dial it in correctly but I will give it another go! If anyone does find an alternative to using museum putty or similar, I would pay good money! I really would rather use something else as I don't like using it for coins with fragile surfaces but I'm having a hard time coming up with something better, and I'm sure many of us have tried.