Ali at Animal Plastics told me to use furniture pucks you can get at like Ikea and stuff. Says they give enough space while still allowing the alignment pins to still work. I personally just use flexwatt on my Ap cages and stack them with no gap and it's worked fine.
0.1 Rio Bravo Pokigron Suriname BC-Gina
1.0 Meltzer/Lincoln Peruvian Longtail het anery BCL-Louie
0.1 Biak Green Tree Python-Pat 1.0 OSHY Biak Green Tree Python-Alex
0.0.1 Super Reduced Reticulated Gila Monster-Dozer
0.0.1 Utah Banded Gila Monster-Tank
0.0.1 Super Black Beaded Lizard-Reggie