I very much agree an 18 foot cage is major overkill. 15 foot males are super rare. You're looking 10-12 feet on average.
Also, I'm sure others will disagree, but I never liked lying to breeders about what I was going to do with their rabbits. I could never pretend to be giving a loving home to an animal and then feed it to a snake. Seems like that also plays into the negative stigma surrounding our hobby as snake keepers.