Those Christmas tree type fasteners really are hard to use, cuz once you snap them in there they're a major bitch to get out! There are actually really cool and easy to use clips made of a heavy gauge wire. They have sort of a flat area on the top that slides on to the 1/8" board you're useing and basically holds on to it from both sides if you can picture that! then theres the
lower" part that is sort of spring loaded and goes into the hole in the door, or whatever, and holds the panel on. I know this sounds weird but they work great! When I do upholstery panels I use "1/8 " door skin" that you get at home depot etc.