Alexis
That's a creative answer, and a good setting to know about, but I 'm confident you'll find a LOT of bright pixels 'bleeding through' from below that will provide a noisy and unsatisfactory result.
The best solution for this is proper use of footprints, such that everything outside the footprint is ignored (set mosaic dataset property "clip to footprints?" = yes). Defining a NoData value of 0 does not work well because the NAIP county compressed mosaics are wavelet compressed (MrSID or JP2000) and there are a lot of black pixels with values = 1 or 2. The zero pixels will be hidden as NoData, but the other black pixels will create an annoying noisy image that will change at different zoom levels.
We published detailed discussion of this in the Image Management Guidebook along with example scripts (and sample data, including NAIP) that you can download from this Group on ArcGIS Online. Look for the "Preprocessed Orthos" example (2 downloads for script and sample data) and note that there are 2 sample datasets - one is edge matched tiles which do NOT have this challenge, and the other sample is county compressed mosaics that do exactly what is shown here. You'll find we use different settings on the 2 mosaic datasets to manage the two different image formats.
For future reference, it's best to start with this landing page esriurl.com/ImageManagement which includes hyperlinks to the Guidebook and sample scripts.
Cody B.