[John H]

Many of the 16th century suits of plate that I have seen do not have a mail skirt. How common would these have been by the 16th century, particularly among infantry equipped with a complete harness?

[Nathan Johnson]

I have seen a painting of Pavia in a book in which a group of heavy infantry have knee length mail under there tassets,I wear one when I'm dressed as a landsknecht but I only wear 3/4 armour.(front rank halberds leveled at groin hight make it a necessity to my mind ) but I don't know how common it actually was.

[Adam Bodorics]

I attach the few I found on my computer in a minute (I'm lazy, sorry). I don't know about how common they were, but they existed. As mail was more expensive than plate I'd think that only richer infantrymen or nobility would use it, and anyone who would have enough money would copy them.
(The filenames are left as I downloaded them, they may be incorrect.)
edited to add: the first picture has a lance rest, so it's trivially not infantry, sorry.