I'm afraid that it
is a hard rule (it applies also to panel lines like on Your Me 262), even if it makes the Leo 2 turret look like a cheese wedge. (
) I believe that there are old posts made by Admins who specifically stated so (though it might take quite some time to dig them out).
As for the wheels - showing of depth in principle would be ok, but for example there are 3 shades used on that external black-ish layer (looks like they might be made of rubber, so perhaps we could call them tires) and their shape don't suggest the need for 1-2 of these shades (after all, they aren't "balloon-shaped" like, say, low pressure tires, so at most there could be one shade for that part that's shaded by track covers and another for unshaded part - but I'm not sure if the SB/FD style demands that the covers put so much shade on the outside-most parts of the wheels).