Wow . you must have picked up 3 or 4 stowage sets , thats a lot of Panther track . I haven't seen the extra armor on Shermans , I think that with the 3 man turret crew having to get out of one hatch ( on most models ) might be something to do with it, sort of like they got rid of the 50cal as well . Churchills have those wonderful side escape hatches for the crew to use if under fire . BUt , I've also seen it on Cromwells , and those are small hatches to get out of in a hurry . Maybe late in war when the Allies worried more about snipers than tank on tank battles ?