If I put a palm rest guard on my MBP, will my hard case still fit?

[newowner]

I am considering buying a palm rest guard and trackpad protector because I noticed it was starting to seem greasy looking...however, I've been looking at peoples reviews of these and I've seen some say that even though the protectors are thin, the hard case for the outside of their mac will not fit over it. Is this true, does anyone know??