Erm, the shields can be lifted when engaging the other tanks to protect the tracks but I think I'll edit every tanks with shields covering the tracks now.
I mean that "shield" on front of the track is a massive design failure, you can ride only on flat ground because of it. You will stuck on every rough terrain, even the smallest hill wil stop you.
EDIT: Mark IV's? What's that?
Mark IV ... grandfather of all tanks, THE Mark IV.
( sorry for ridiculous ideas, I don't know much about how tanks works etc )
Then why you try to create one ? First level of any design is to know how it's work, cars, planes, ships ... everything. Look at modern tanks, how they look, watch movies with them, how they move.
And again, please don't use attachments.