Check the actual composition of the MDF that you are using. I know that there are a number of kinds of MDF and some people use the definition loosely. From Jason Susjnara:
The spoilboard that comes with the machine is 32 lb density and the wasteboard is 48 lb density. If you are not machining 5 x 10 sheets, you can use a 4 x 8 wasteboard. I belive that we have to machine both the spoilboards and the wasteboards here to the correct dimensions because we order it oversize. Hope this helps.
I specifically asked my salesman if the 1/4\" wasteboard he could supply was actually 48lb density. He confirmed that it was and I bought it. My guage reading doubled from about 8 to 16. I also purchased a roll of plastic film that I will use when I am cutting smaller parts to seal off that part of the table where I don't have parts. We have a CS45-510 but most of what we cut is 4'x8'