speaking from experience, heats going to be an issue. make sure you have a small thermometer to keep an eye on things for the first while. also do a bit of research on how to most effectively use those fans(exhaust, intake or what have you). and depending on how you mount them and the speed, the noise from vibrations voids the whole stealth of it and will also drive you crazy. i have 3 3'' fans running slow and its still abit loud. i hung them with some bent coat hangers and this minimizes excess noise.
good luck with it