Inverted faces after using the mirror tool is a problem that Max had for a while now. To avoid flipped faces, just use the mirror modifier rather than the tool. To see the flipped faces in the viewport, apply a Reset XForm to all your objects and it'll show you the flipped faces in the viewport as well, once you collapse.
First time posting WIP here. This is one of my portfolio projects I have been working on. Resurected it recently since I lost my job and need some good portfolio peaces to show. I havent dont any tanks/APC's so I would LOVE some feedback/critique! Basically this is a "near future" Russian APC design I came up with.…