The rules with big heavy high powered binocs is COMFORT. You need the mount to fully support them because you'll fatigue trying to hold them, and you need to be in a neutral, comfortable posture so you're not straining your eyes. Bending over, crocked neck, bent backwards, hunched, etc all constrict bloodflow through your neck to your head, and you will severely affect your eyesight, meaning you won't be seeing everything in the binocs.
Parallelogram mounts are classic, make your own, the production ones are soooo expensive. People also make articulated mounts that go on a rotating, tilting chair so you're always in a neutral seated position. Finally, big saddle mounts are the next best option, they support the binocs well but aren't as good for looking at high altitudes.
All of the 25x100 binocs are roughly the same (mechanically at least), you have a 1/4-20 photo tripod thread on that center stalk, all of the big binoc mounts have dovetail shoes that will let you mount the binocs.
Or, sell everything and buy my set as a package
https://www.facebook.com/marketplace/item/27220417774238249