I tried my 2mm top deck with the 3mm chassis for the first part of a meeting and when I changed to the 3mm the car was so much better. This isn't to say that I could have changed the setup, but I believe that on carpet with foams you need to go as stiff as possible. The hara 2.25mm top deck will probably have more lateral flex than the 2mm kit one so I'm guessing that would be even worse for carpet and foams.