I've been brand loyal to Pioneer head units for a very long time now.  In the last decade or so, the NEX series.

It used to be the mp4 files had to have a very low data rate to be compatible and that is something i accepted over the years.  Even as i upgraded by dvd's to BluRay, and then my BluRay to UHD).

Recently (quite by accident) i copied a higher bit rate file to the USB thumb drive without realizing my mistake.  When i got in the car, the picture was much better than my files from 10 years ago, and I almost immediately realized my mistake even as i was dumbfounded that the 8500 was playing the file (instead of giving an "unsupported format" error...)

So my question is simply this:  What are the best/maximum settings for creating mp4 files to play on the 8500NEX?  Dimensions, data rates, etc. 

Thank you in advance!