I may be purchasing a rhp sooner then I thought bc of last nights air temp but I think I'll have an issue with installation. It will be going in a v400. The cage is made with a grove in the top for stacking cages but that grove leaves a bump in the middle of the inside of the cage. I'm assuming I need a flat surface to mount the rhp. Is this correct? If so I might need to buy PVC to run inside the top to make a flat surface to mount to. I would like to also get one for my v211 but there would be no way to mount it do to the air vent. I'll have to wait to buy an rhp for her until she is bigger and buy a t8. So for now it will be ceramic heat emitter, which I'll also be using for the v400 until I get the rhp.