I have only worked on the upper hull to present, but I think the kit comes with the angled rear hull bottom which needs to be the smooth curve type to exemplify a Baldwin trait. I should have a few lying around to use on this build.
Here are some shots of my building up of the thickened turret armour.
As original...

Here is the finished result as shown on a M4A3 turret I had made a couple of years ago...

The area marked out.

MagicSculpt is used here...

The finished part smoothed off. To this I added a cast texture from liquid cement.

This undershot gives a view of the thickness. Only needs to be about one scale inch...

This pistol port is to be removed.

Carved off...

Putty added...

Squeezed through. I let this set so I could sand it back.

After this, the kit antenna pot on the front right glacis will need to be removed as the Baldwin type is of a U shape when viewed from above and frontwards.
The kit type is of the Pressed Steel Car variety.
More on that later

Brad