Max thickness of material that can be cut is around .5", even with the tray out. No way to cut anything that thick as the laser can only be focused down as far as the where the surface of the crumb tray would be.
Well… the focal point of the beam is where the focus height sets it. The beam diverges to the same degree on either side of that point. But even diverged, it still has plenty of energy. Remember, to cut through that 0.5" thick material, the focal point for the beam is going to be at the top of the material. The bottom of the cut is going to be 0.5" away from the focus point.
Cutting something like foam that doesn’t require a lot of energy should work just fine. The edges may not be that clean, but it ought to cut it OK. If it’s 2" thick, I’d prop it up so it just clears the printhead and tell the GFUI it’s 1" thick. That’ll set the focus in the middle of the 2" slab.
Of course, it’s important to know what the plastic actually is. Just putting some random unknown material in to the cutter does come with risk. Maybe not a lot, but not zero.