In article
,
Kyle wrote:

seeing if I can slip a mini-plate
behind the wall, something maybe 1/2" thick, an inch wide and long
enough to distribute the weight of the rack and towels over a greater
area of the wall.

I've done this, not for a towel rack, but the concept works. I put
construction adhesive on the part you're calling a mini-plate, and
provided a means to temporarily pull and hold it against the inside of
the drywall while the glue dried.