Been falling behind on this thread, but thanks to many of you - gda13, tclausen, LeRolls - for the kudos on my macro adventures!
Last weekend I went down the "flash-diffuser-from-a-Pringles-can" route. I quickly figured out that my 90mm plus tubes was too long for a single can, and will require a telescoping setup made from two cans. Since I only had the single can on hand, I went back to the Pentax 50mm F/4 Macro with 50mm of tubes. Using the onboard flash with this setup makes a really, really light 1:48:1 (greater than life-size) set-up. After some tests, I settled on F/14, 1/180s and iso 200 at MFD (bugs standing on light, reflective surfaces might require iso100). Recipe: head into the garden, approach bug slowly, very slowly, and when focus is reached, hit the shutter!
Not A Jumping Spider: Red Eyes #2: Timini The Jumping Spider (#2): Sans dessus-dessous / Upside-down:
This last one was shot while holding the camera upside down as the bug was hanging underneath a leaf.
I'm having a blast with this camera.