no stacking, just a straight handheld shot.

Very nice. I've found I can get the sharpest images at 5:1 by opening the aperture to around f/4.5. At that aperture, however, the depth of field is incredibly shallow and I have to use focus stacking to get a good composite image. Finding a focusing rail that you can stand vertically is a bit difficult, but there's one by Minolta that you can sometimes find on eBay, or you can build your own out of a regular focusing rail. Another option is to mount the pedipalp in a cuvette filled with hand sanitizer and use a regular focusing rail to shoot horizontally. See https://www.youtube.com/watch?v=izqFaia_8bU. Or you can just stick to doing a handheld shot and save yourself the trouble :)

I wasn't aware of that technique. I do have all that I would need to stack vertically but I'm lazy. I acquired a Stackshot that I really need to start using, I think they can be used vertically though I haven't tried it. I took this shot at f/8, that is a fairly good trade-off for diffraction vs depth of field. For smaller palps I sometimes have to open the aperture a little more than that or diffraction blurs the image too much to see structure clearly. If I was ambitious I'd mount one of my microscope objectives on my camera like you see at http://www.photomacrography.net/. So much incredible work on that site.