You will be fine. I put my Colombian girl in a 48x24x14 Pro-Line cage when she was about 22" and she loved it. I just gave her a hide on the warm and cool side and of course a water bowl. Depending where you live, you might just need 1 large water bowl. That's all I use under my PH3 Pro Products 65w RHP and it creates plenty of humidity. I personally don't have any heat tape on the bottom, I just use the RHP on a Herpstat and she has been fine for just over 3 years. I am going to get her and my sunglow girl AP T13s this summer and then just give my Pro-Line cage to my BP though as I want the added height and depth for my girls. I probably will have flexwatt put in on those cages though but not sure if I will use it or not. Might order it from Ap or just get some THG tape from RBI and do it myself as THG is supposed to run a lot cooler and not get so hot as flexwatt. Anyways, you'll be fine as long as you give the boa a couple hides. They aren't nearly as shy as BPs and definitely are more gung ho eaters.