I bought the PE Foam a few days ago, and to KK's credit, it was delivered extremely fast and on time.
However, I am not sure how effective the PE Foam is in changing the sound of the switches. I had hoped it would produce a more poppy/marbely sound as PE foams are usually used for that, but this foam didn't do anything to my keyboard. The foam is very thin and it could be why it wasn't so effective.
If you are buying this for K8 Pro, know that you will have to remove your stabs first before installing the foam or it won't sit on the PCB properly. It also won't lay completely fat and will have 'air pockets' but that doesn't matter and you will be able to install the switches no problem after you apply the plate on top.
The product is great but it didn't produce the kind of sound I wanted and that makes me disappointed.