Please be mindful that i didn't draw any chainmail underneath, first bc im lazy, but every armor from XV century had some : over the gambeson, under the plate, fully or on located areas. They also used pants gambesons.

Also this is just one example, XVth had so much armor variations for any of the parts above

Here're some references i like to use :

-> The Evolution of Knightly Armour

-> Age of Craft