I fill it every morning actually, its part of my daily routine.If any water is left in the unit, i dump it out and refill with fresh cold water. Because of the positing in the cage, and the size of it (30x30x48) it is in between the two larger plants in his cage- its transparent to him really, and a non issue in my mind.
I actually tried your suggestion first, i had flexible piping that ran from the base of the unit out through a hole, and up the back that enabled the mist to fall from above. The project was a failure, the humidity was building up on the bends of the piping and just dumping back down onto the unit.
This was essentially a temporary solution/test until i ordered my misting system. It is currently in the mail and should be here by this weekend. I will most likely remove the humidifier completely, as it will not be needed. Overall, i consider the experiment a success, PENDING you are OCD about cleaning and maintaining the humidifer.
Again let me reiterate that i would NEVER consider using a cheap $10 crapola humidifier such as the vicks for this. The humidifier that I purchased is top of the line with automatic digital timers, a felt filtration system that is replaceable, and 100% silent operation.