So I can address this firsthand, as I work at a museum that has a Panther Ausf A. that I climb in often (often enough, I should say)
The Panther is comparable in size to the M60 Main Battle Tank, yet the turret is twice as small for a gun roughly the same size as the 105mm M68. The Turret ring is the real killer here. You have to fit 2 men at their widest part and one whole man minus head and feet(*) in a space no larger than 4 feet (slightly more than 1m) across. And while the quality of optics in the Panther are fantastic, their application is garbage. The commander gets the most out of everyone and he can ride in an open-protected position, but there's much blocking his view like the ring skate for the machine gun and the blocks where the periscopes protrude from the cupola. The periscopes themselves are small and don't cover a lot of ground. You're blind if anything is closer to you than 20-30' at ground level in front of you. There are also fairly large gaps in the coverage these periscopes in the cupola provide as well. The Gunner gets shafted, while there is a variable zoom setting on the telescopic sight, the gun blocks your right-side fov completely. The commander pretty much has to scan for targets since you're too busy looking at your muzzle brake to do much else. The loader...that poor man, gets one periscope, and its fixed in an asinine position looking slightly to the right of the turret. Spending a little time implementing a rotating peri mount for the loader and a unity periscope for the gunner would increase the SA of the crew by threefold.
Honestly what was Germany thinking when they designed the thing? Turret rings too small, optics are poorly placed and barely useful...
*The turret has to accomodate
-The Commander's body, whose head is in the cupola and feet are below the turret ring, so the ring has to only accomodate the lower calves/ankles of the commander.
-The Gunner's upper torso
-the loader's entire torso if not more depending on where he's accessing ammunition from