The two I'm having a problem with aren't going to fix their core deficiency no matter what I upgrade. They start with their best penetration shell, but it's just grossly inadequate.
So while it looks like a tank it definitely isn't one.
I like them because they're funky little things but they really shouldn't be fighting other tanks
(1) If the Germans had screwed around and given the French a chance to raise their armour divisions it would have been a very different war