I do have sources for everything I said.
The lack of a turret floor was considered to be a design choice, not a disadvantage. e.g. the Panzer III was upgraded and improved many times over the years, with four different guns installed, but it was never given a turret floor.
This WW2 photograph is reproduced in Spielberger’s “Tiger” volume. It shows the inside of the Porsche vehicle’s turret; or, rather, a wooden mockup of the turret they intended to build. Every panzer started out as a wooden prototype which was used to test and finalise equipment layout.
We are in the region of the commander’s feet, looking forward at the gunner’s chair. As I point out on the photo, there is a crossbar passing under the gun, apparently identical to the one in the Tiger (H). It also has the same elevation gearing over on the right. But there is no floor and no gearbox. Instead there is a large shell-catching bin, connected to a central post which doubtless would carry the electrical connections to the turret.
David