Yes, I agree with you Steve that the problem is sometimes seen as "spoking"-- those stress lines radiating out from the center of the tape pack, though I don't recall whether spoking is caused more by a slot in the hub or by expansion and contraction due to changes in humidity and temperature. I do know, though, that I've definitely seen tapes with a visible crease that is clearly caused by the pressure of the wound pack pushing the inner windings into the slot. On occasion the crease has been pronounced enough to cause drop outs in the last few minutes of a reel-- not a problem if the tape hasn't been recorded all the way to the end-- but sometimes a problem.
The array of conditions and problems arising with open reel tape is interesting and sometimes surprising. Not to wax romantic over open reel tape, but seeing all these conditions is more interesting (to me) than having a crashed hard disk or a CD that's unplayable.
Anyway, call them what you will-- "reels with slotless hubs" or "slotless reels"-- in another few years talking about them will probably get some of us about as far as mentioning LPs to a teenager does today. People won't believe we actually put up with a linear format.
Why do I think the question about slotless reels was tongue in cheek in the first place? :>)
Best wishes all,