Actually, I'm trying to get mine thinner than factory. The ones I have are on the "puffy" side. Flattening it on a table with something heavy over it might work, over time. Too much weight too quickly I would fear causing a blowout. I have more hope for the vacuum thingy.

(hopefully I'll find the other un-unpacked 'sheet sometime over the weekend to give it a try)

I've used the vacuum thingy on stuff like a pack-towel and spare winter socks. Pretty sure I got them more compact than the "Ham Press" ever would have.