The biggest problems I have with the Tetrarch are the aim time and lack of view range. I put binocs on it because optics aren't enough to put it on par with the tiers it sees.
First battle in it was quite clubtacular:
The penetration on this tank is excellent. The normal rounds tear through T18s and FCM36 Pak40s like butter. I don't think it even needs gold rounds at all except for the occasional Pz. II J.