Ah, the RK05 - evil incarnate. I mean, a disk drive exposed to the air?
Out There Somewhere [tm] is a picture of a human hair compared with the
head clearance; yikes!
IIRC, the picture showed that even a smoke particle or a fingerprint is bigger than the gap, never mind the hair.
Once I had to take a PDP-11 accounting application from $EMPLOYER's NJ office to a customer in KC. It fit on a single RK, so I took two identical disks just in case. This was in the late 70s. They were already X-raying carry-on luggage then, and I had a Bad Feeling about what might happen, so I said no.
"No problem. Does it open up?"
"Well, yes, but dust will ruin it."
"Well, what should we do?"
"Trust me?"
"Well -- okay. Go ahead."
Of course when I got there both RKs were scrambled completely, so I took the next plane home. The next weekend, a colleague took the application on the same flight. On floppies. Floppy floppies. Lots and lots of them. It installed fine. Of course it took him all day and much of the following day.