What's customized about it?

The most important change is the shorter arm.

I've been looking into this for my C8 and am glad to see it works well for
you.
Could you describe everything in more detail?

I highly recommend it as a second mount for a C8, it's a low to medium power
portable visual mount for the C8, but you got to have another stronger arm
to
fully use the power of the C8.

What kind of tripod are you using, etc?

Gitzo G1415.

Oldfield