This is my Lego StuG IV. The German StuG IV evolved from the success of the StuG III, which was technically an assault gun intended to support infantry, but excelled as a tank destroyer. The lack of a turret allowed for thicker effective armor and a lower profile, in exchange for gun mobility. The StuG III was based on the Panzer III chassis, and naturally, the StuG IV was based on the Panzer IV chassis. With this in mind, I built in the ability to remove the hull from the chassis and suspension, as I showed in https://jonathan-pigott.com/2017/04/04/lego-panzer-iv/
The big panels are called Schurzen, which helped negate the effects of HEAT rounds, which would detonate prematurely and with less effect on the hull. I also included a neat shielded machine gun on top for the loader/assistant commander.