First - great job on the Sherman!
Thanks!!! For the tracks on the outside I the plastic tracks from the HL Sherman (thanks Jeff). I cut off the teeth. It looked in photos like the Marines had removed them prior to welding. I used hobby grade CA glue and used insta-set. They are holding firm. If they stop holding I will probably resort to plastic weld or epoxy putty.
I like attaching accessories to the hull with silicon adhesive (Goop), as long as the piece is large enough to hide the glue. The part needs to be supported until the glue sets. Assuming the part is sturdy enough, it can be removable with slow and constant pressure. In my experience, damage to the plastic/paint has been minimal.