out of curiosity i looked at the pre made C&C cages on the linked site, i had no idea you could get them made for you so i thought id check out what they look like.. but wow
that is just way over priced. even the ramps are obnoxiously priced IMO.. & awbat3 is right.. you can easily make something yourself, thats why C&Cs are so great, they are cheaper and easy to build.
hanhan27 i would think that if you wanted to have the walls taller for the winter only that would be ok but you still would need some form of ventilation as i know they do require that. maybe punching some holes??.. another option that may be a bit easier that i have read people have done is using fleece. i actually use a regular blanket to cover a portion but not all of my cage. if using fleece just make sure it is not too close to any lamps you may have of course as it could be a fire hazard too, i have seen people make liners that were fitted to the cage specially with holes made so it doesnt come in contact with their lamps, or you can also make them to only cover the sides, it would probably be easy enough to just cut fleece to fit and use clips or ties, i think that would let enough air through but still keep the warmth in.