It should be fine just to hang inside it, this sounds like a very good idea
Although sealing it inside the airbox would be better I think, to stop it drawing in warm air from above.
Take your MAF out and let the car run for a bit without it. Rev it up and what not, let it idle for ten mins, only then re-fit the MAF. You should get a killer induction noise with a K&N in an enclosed space
