Probably a long shot but does anyone have plan drawings for the later welded lower hull (with rounded instead of flat angled rear) that shows all the hatches and everything, either already in 1/35 or in a format that can be scaled to this?

My main point of interest is being able to exactly replicate from scratch the rounded shape of the rear section below the tow hitch plus all of the drain plugs and hatches, the 2 compartment doors themselves will be omitted in my build.

Son of Sherman includes bottom views:

http://www.ampersandpubco.com/son-of-sherman-1



Example (not of M4A1):