Hi Grayhawk
AFAIK - you can't simply override entries in the default config.bin file, but you CAN modify a standard unit by way of a config only addon which will have the same effect.
I am about as far from being an expert as you can get (having just started looking into config files today ! ;D ), but from what I can tell by looking through the main config and a number of addons each lower level of class simply modifies the class above it in some way. Anyone can make a new class (and thus a new lower order item) simply by changing the class immediately above it in some small way.
So in your example - you have defined a new class of vehicle, different to the standard M1Abrams by a change to the display name only. You might call this a M1DisplayingAsTest. To get this to work you would have to add the line
class M1DisplayingAsTest: M1Abrams immediately before your change.
That's my guess and remember - it is just a guess !
(But a reasonably informed one !)
The above all being said - I happen to have a sub folder with a number of replacement files for the standard config.bin file. I dl'd it years ago, but have only just gone back to it (today !) to see how it works.
From what I can remember, if I rename the new folder BIN and move or rename the original BIN folder then the new files get read by the system as if they are the default. :wow: The good news is that the new files have stored the config file as a cpp - which I can read and edit ! ;D
Over the next few days I intend to get to work seeing just how much damage I can do to the basic workings of the game. New default recoils, binoculars that zoom, better souds for my favourite guns - it's all going to happen.
Stay posted !
Roni