Thanks @decooney . I would have to email them, because I don’t think they talk to people on the phone anymore unless they want to buy something. The last time I emailed them about something, they were in no hurry to get back to me, but I guess that is what I should do.
As far as stacking, my preowned SLP05 was manufactured back when they were putting those indentations in the top panel of the power supply for the preamp feet to rest its feet in. But I was sort of under the impression that they were no longer building them that way.
I did, just now, consult the owner’s manual Cary provided with my preowned unit, and, as you pointed out, mine says the identical thing under the heading of "IMPORTANT SAFETY INSTRUCTIONS."
But then on page 15 under "BASIC OPERATION" it says "You may wish to stack the preamplifier on top of the matching power supply." Then it goes on to say that either/or is okay. You are right--I should email them and express my concerns about stacking a component on something that gets as hot as that power supply gets. Either that or just not do it. I am thinking more & more of doing option 2.