Print glued with Muck or LaminAll to 1/2" Gator. Although 3/16" Gator will do with wood bracing frame on the back, but that's too hard for one so work-adverse as me. For moulding with shallow rabbets the 1/2" Gator forces to use offset clips instead of Fletcher points, bummer.
I had been using 1/2" gator for my larger work but was running into the small rabbet problem (1/2" depth) just like you.
Moved to the 3/8" product and that works really well. Price is similar,a couple of bucks less. $57.00 here in eastern Pa.
Don't you just love those small 1/4" x1/2" rabbets when working with a large pano.