You will need to experiment to find a sandwich that works for you. Different companies have different thicknesses of folders. In my collection they range from just under 1/8 inch thick to 1/4 inch thick. That's more than the thickness of a plate.
I tried replacing a plate with the Spellbinders embossing mat, using shims, replacing a thicker plate with a thinner one...there are many options. My best results come with using the embossing mat in the mix.
SU won't be able to help you since it's their machine and they will only help with their own products.