How to securely mount it on tripod? I know there is a mounting screw on the lens but I don't trust it. So, I rather look for something bracket either custom made that holds the camera and the lens together.
If you look at how old wooden LF camera tripods mounts are used to attach very much heavier cameras to a tripod, you'd realise the Sonnar lens tripod lens mount is sound, balances the body & lens.
How to securely mount it on tripod? I know there is a mounting screw on the lens but I don't trust it. So, I rather look for something bracket either custom made that holds the camera and the lens together.
The built-in tripod collar of Sonnar 180 is a very nice thing, never regreted to use it. Using the 645 back with my Hartblei 688 camera I could also turn it in portrait orientation.
As others mentioned, the tripod mount on the Sonnar 180/2.8 is plenty strong for the combo. After all, the Pentacon Six is not that heavy in term of medium format cameras.
On the other hand, there are plenty"Dual Camera mount tripod bracket" on your favorite e-commerce websites that costs less than $15. If you have to have that kind of peace of mind.
I just measured the height difference between camera's tripod mount to the sonnar's tripod collar mount to be 20mm.
Yes, I could get a dual camera mount and possibly get one of this (30mm long) for the camera
and drill a slightly wider than 1/4 inch hole and secure everything tightly.
But I have found something like this for Sonnar 300mm f/4 and I wish they made one for 180mm too...
I have this lens and on my copy the tripod collar locking mechanism is not very secure, it wobbles, it's a hindrance to using it. Other lenses I have with tripod collars perform much better. But it might just be mine.
Using a metal bar with groove that accepts two tripod screws won't hurt you. I think it's better to use a 3/8th screw directly on the Sonnar if you can rather than adapt it, that can be a point of failure if the metal is soft and also they make adapters in different lengths.
Another reason you would want to use a bar like this is to balance it on a gimbal. Could be more applicable if you plan to add a teleconverter.
I would never trust that tripod collar on the lens and I was looking for some safer solutions. The tripod collar and camera's tripod mount is not on same level so solutions such as this could be optimal.