Great summary Garry. You've got me looking at geared stands now :-/ I've been through a number of different boom options - starting with the traditional boom arm. This works ok, however as the spigot is never vertical, the light will sometimes rotate around it if the light's mount point isn't roughly at the centre of mass front-to-back. There's less moving parts with these though. I've never owned one of those worm drive arms, but have used them and agree they are under-engineered and woefully inadequate to hold a full size studio flash head. I solved the mounting issue with a C-Stand and boom arm with a grip-head on the end - which means the light always mounts to a vertical spigot - as long as you adjust the grip-head to match the arm angle of course. It works but is very time consuming to set up correctly, as adjustments to one angle, need adjustments to others, and each time you adjust these things you need to lower the whole rig to get at the various parts of it, and it doesn't completely solve the problem as the boom arm sections can also rotate if not tightened down excessively. Also, the boom arm I have, is made of monkey-metal, and the threads for the mounting bolts are tapped directly into the castings, and they don't last long. I have bonded brass liners into mine now (after drilling the holes out larger) and this works ok so far.
My current favourite solution is a 4ft cinema camera crane. Specifically, a ProAim Astra 4. This has a pole that takes standard barbell mass disks so the balance can be adjusted to within the mass of whatever the smallest disk you have. It comfortably holds my Falconeyes 1600TDX LED spot at 5kg, and has no problem with a SF 600 at 3kg. Also, the platform remains horizontal as you raise and lower the boom angle, so the light always remains at the angle you set it at. It's mounted on a dedicated stand, also from ProAim that is built to take this and larger cranes.
View: https://www.instagram.com/p/CHoQWjNgp-f/
View: https://www.instagram.com/p/CLznbEnAZaw/
(2nd picture)* **
Incidentally, the footprint of my Lencarta supplied C-Stand is a bit wider than a regular light stand at 72cm, however the stand reaches well over 3m in height (technically it's not really a C-Stand as they are named for their height of a hundred inches or 2.54m ) so the ratio of base width to max height is too low. If you use them at ~2m though they're stable enough. I have used mine at 4m (with the extension pole vertical) to get a light though a first floor window, however I would only ever attach a Speedlight or AD200 to it, and it has to be manned: I wouldn't trust it to stay up in a stiff breeze on its own in this configuration, even with all the sandbags in the world on the base. Another problem with these C++stands is their minimum height, at 1.3m is much higher than a regular light stand. This creates problems for transport. I have no idea why they are almost always chromed up, and for product photography where reflections of shiny things have a habit of showing up in the picture, I've often had to resort to throwing a black cloth over it.
* Also in this pic - see an example of rotating the spigot in a light stand by 90 degrees - to connect a Super-clamp to hold the screen.
** that isn't a boom arm on the C-stand in this pic - it's just the simple extension arm.
