Foil chimeras do not count towards the 6 card per limit for chimera. Not that this is exactly an OP bug, but it's almost certainly not intended. The reason probably stems from the fact that the foil chimera has code 75c, whereas the unupped chimera has 560 and the upped chimera (normal) has 74g, so I guess it's treating it as a wholly different card.
So yeah, I'm going to smash face with my 7 upped chimera deck until this is fixed :p