I've been out of the project for a few weeks, but figured I'd jump back in.
Here are two that I think have room for improvement, but mostly were me pushing the limits of what I have on hand.
These were all taken on my D800 with an ancient 55mm AI-converted Micro-Nikkor-P f/3.5 lens, my personal favorite macro lens. I have a bunch of Nikon F era(probably 60s and 70s) macro accessories. The one thing in storage that I'd love to pull out are my PB4 bellows, which in addition to having a lot of extension do incorporate stop down by a cable release for easy full aperture viewing.
Here's my full stack to get to this one-
PB-11, 12, and 13 rings stacked, which are 8mm, 14mm, and 27.5mm respectively(49.5 total extension). The Nikon tubes are nice in that they keep full aperture viewing. On top of those is a generic set of tubes that measure 60mm to me. Then I have an M2 tube, which was shipped with the 55mm Micro lenses and is 27.5mm to allow them to go to 1:1(the built in helical is 27.5mm). The generic tubes lose stop-down coupling, so to that stack I added an E2 ring, which allows stop down by a cable release(or rather push/lock the release for open aperture focus, release for stop down). It's also a 14mm tube.
This is a total of 151mm of extension. Adding the helicoil racked all the way out gets to 178mm, which I think should put me in the 2.5x lifesize range, but I really need to measure focal plane to subject to calculate exactly(if you really want to get exact about this, and forgive me if this has been mentioned, but your camera should have the Φ engraved on the top plate to get exact plane, and magnification is measured from here to the point on the subject in focus).
Lighting is by a couple of strobes. I need to get a stronger power pack out, as I had to raise the ISO to 1600 to get the exposure in the ballpark. The lens nominally was set to f/32, but I think that's an effective aperture of f/160? Forgive me for being fuzzy on the math.
Then, just to get fun, I stuck a 1.4x teleconverter on the back. As some back of the envelope math, if you place extension tubes in front of a teleconverter, you can treat it like the TC multiplies the effective length of the extension tubes by its magnification power, so this would give me ~250mm of extension, or nearly 4x lifesize.
Miraculously, I did this all handheld. It really should be done on a tripod with a macro focusing rail, and I'll try that later.
This also has the lens nearly covering the subject. Reversing should help with that, and it's something I'll play with later. I do have a BR2 reversing ring, which works with 52mm filter thread macro lenses.
And here's the full unwieldy set-up