Hi James what do you mean a SturmHetzer? I didn't know there was such a thing....isn't that the standard 75mm gun?
It's just a short 105mm made using the Flamethrower but pushed through the mantlet from behind.
The regular 75mm is probably twice the length I think and not as chunky.
There was no such thing though. But I just model and play for fun and enjoy the chaos of rivet counters melting with anger XD