I run that same set-up in my top two TDs but have vents in my BT-7 because I want all the camo help i can get.and with the guns on that a rammer is kind of redundant. Most people would say don't waste your time on putting permanent stuff on a tier 3 but I growing to love my BT... unless some bastard advances on Campinovka, then I'm stuffed.
Unlocked the last of Tier 3 last night with the Vickers Medium. My god, what a piece of shit that thing is. Suspect the 6 pounder makes it a decent faux TD but you need 1200 Experience to unlock it and tthose 1200 would be extremely painful.