[remy_martian]

Looks like the premium caliper senses the current for consistent clamping force.

My concern with your technique is not being able to release the parking brake with a lower 12V battery voltage than when you set the brake.

For your next experiment, clamp at 13V, release at 9V...if it does, Bob's your uncle.

 

[remy_martian]

Is that by design or is yours simply not properly adjusted?

The caliper is the easy part. You need to find a way to mount it.