Thank you very much for your reply, Ellis Vener. You have been helpful to me before on other forums, and I very much appreciate your expertise. You help me here by revealing to me what I failed to consider--and that there are many variables I have not yet figured out how to quantify (and that might be moot, given my circumstances). So...
I will try to get closer to learning what I need to know by adding some information and then asking a different question:
My t.1 flash durations are always around 1/588 or shorter (faster); two Paul C. Buff Einstein units per exposure synced with Buff CyberSync Transmitter and Tranceivers, usually firing very close to full power.
When I use the 50mm and 100mm lenses, the camera is supported on a Bogen/Manfrotto 410 geared head sitting on a Gitzo Series 3 aluminum tripod with center column extended just a few inches or so; when I use the 400 mm lens, it's attached via lens collar/foot to a Gigapan unit (operating in rigid mode with 3-second pause between position shifts and three-second pause after each mirror-lock-up) sitting atop the aforementioned head and tripod.
Under these circumstances, does using mirror-lock-up make a difference? (I fear that I further reveal my ignorance by hoping that this question is any more answerable than my first one; please don't hesitate to straighten me out!)