This is a 150mm howitzer
The Sturmtiger is a 380mm rocket

Most of the google search for Brummbar ammo turns up Sturmtiger ammo, and I know the two are not the same. But it would seem difficult if not impossible to load that gun inside that turret.

I'm not a WOT gamer , but I glimpsed a Soviet T44 mounting the 122mm gun -- Yeah . NO WAY .
....
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I understand the "difficulties" in actually mounting the sIG33 gun into the Schmalturm, but for the sake of the build, it's no more unrealistic than mounting an 88mm as the turret ring is too small for it. I'm just building for fun and I like the looks of it.

And the periscopes do clear the armor plate. The plate comes up just over the vertical plain of the cupola.I would have preferred to use one of the PE sets for the turret roof (and then matched the sides for scale, but no one seems to have any in stock.

I used Evergreen sheet for the stand off armor. 1.5mm I think. I'll have to measure later tonight. I'm thinking of making an enclosure of some type on the rear deck for infantry. I've seen it done on some very late war Panthers but I can't find any picture of actual vehicles where you can see inside the enclosure to see if the deck vents are protected. I could probably come up with something that would work, even if it were along the lines of the AA armor used just over the vents.

I was thinking of putting this in a Leningrad/Stalingrad type scene circa 1946/47 alternate time line idea. Maybe in front of a destroyed clothes shop or department store as a tip of the hat to Enemy at the Gates. This Panther II was from the Cyberhobby white box and has the Volksturm infantry with it, which really aren't Volksturm IMO. They look like healthy military age men, not old men and boys. So I was going to use them in the dio along with a tank commander and bow gunner. I like the idea of the ammo trailer, just have to find one, then make the Panther II tow hitch as Dragon never included it with any of the releases. It's significantly different from the kit provided hitch.

I'd thought about opening up the armor plate around the optics but I though the vehicle would have been a rebuild of a Panther II and with the range I figured it would be used within, they probably wouldn't be needing the optics other than a simple range finding optic. I might still open them up a bit, maybe by bending. I'll see how it works.