Aprilaire 500 Installation Angle

Hello. I am looking to install an Aprilaire 500 humidifier and have a question about installation at an angle. I have read and understand that the humidifier needs to be installed level in order to ensure that water flows evenly through the water panel but I was wondering if installing it at a slight vertical angle would be OK. The reason I ask is that my HVAC system is in a pretty tight area and the return plenum, where I intend to install the humidifier, goes up away from the furnace at about a 5 degree angle in order to avoid a ceiling joist. If I install the humidifier on that plenum it would therefore also be sitting at about a 5 degree vertical angle. Picturing this in my head I would think that this would still be OK as long as the humidifier was level (horizontally) because the water, though it may pool slightly at the top of the water panel before reaching the holes to travel down through the panel, would still ultimately hit the holes evenly and then be distributed evenly down through the water panel. However, I wanted to ask the question here and get some input.



Also, if it is crucial that the humidifier not sit at any vertical angle, is there any method or product for extruding the plenum a bit to create a flat spot to install the humidifier that has no angle?



Thanks.

Aprilaire 500 Installation Angle