Cases for Telescopes

The value of 110 mm +/- ca. 1mm (same as in the Mark V) was measured on a refractor. The small error margin of the measurement is caused mainly because of the diopter adjustment. Because of the not-standardized position of the field stop in eyepieces, it is always a good idea to plan with a security margin of some more millimeters.

You can use
Baader Hyperion DT-Ring SP54/M52 for DTAdapter II&III and Hyperion Eyepieces # 2958052
to get from SP54(female) to T-2 (female), then you can screw this adapter to the T-2-thread of the MPCC and have a male M52-thread on the camera/eyepiece side of the MPCC.

But please do not ask about the correct distances for a camera lens, we never tested this under the stars.

Yes - even if you might be able to reach focus without the 5mm extension, the sensor would be so far away from the distance for which the lens is designed, that the quality would suffer.
So, we highly recommend the extension.

This depends on the connection to the pillar below. The short pillar itself is made of massive steel, this part itself can easily handle ~100kg of weight, the question is how solidly you are mounting it onto your pillar.

We do have four different Nikon T-Rings for different camera models:
https://www.baader-planetarium.com/en/catalogsearch/result/?q=nikon

Regarding required extensions, we highly recommend to look at our Digiscoping Instruction Manual:
https://www.baader-planetarium.com/en/downloads/dl/file/id/444/product/0/digiscoping_camera_adaptations_for_afocal_photography_and_eyepiece_projection.pdf