Well I did it. Deflated, broke the bead, kept the tire on the wheel, wangled the valve stem out, put the rimstrip onto the valve, put the valve back into the rim, and then worked the rimstrip under the tube all the way around.
It was a little messy because the sealant was fresh, but I was able to seal/seat it back up with just a couple strokes of the floor pump.
When I looked a little bit, I didn't see any obvious dimpling on the tube. I suspect it would have been fine, the tube would have been held firmly in place at both beads, and no riding forces would make it move and get cut from friction with the spoke holes.
But I got peace of mind now anyways