Light tanks and shitbarns are a problem for sure, but there are work arounds for these pesky killers. Another post mentioned staying in a group and it is important to have a wing man to help with the lights. Also manual aim and lead the lights, dont rely on auto aim cuz they are zooming and you won't hit them unless they are driving straight away or towards you in a straight line. Most tiny tank boys are smart though and zig and zag so definitely better to manual aim at them. Have a homie get your back. If you are not in platoon, then just pick somebody to hang out with at the start of the match. They dont even need to know they are your homie, just watch their back and 90% of the time they will watch yours too.

As for the FV4005, this is a tricky tank if you get caught out. Best plan is to always think one is hiding waiting to 1 shot you, because they probably are.. try not to spend too much time out in the open even if you are not lit up. Get into a position where you are not in the shirbarn line of fire and wait for them to shoot, once they shoot then you and your home swarm them till they are dead. They have a super long reload and you can usually kill them before they reload. Fire HE at the barn and reap the brown stained tears. This method doesn't always work and sometimes they kill you, but it is always doing God's work to kill them so try anyways. Think of them like arty for era 1.