Angle Constraints

Hello all,

I am having a problem with a project I am working on. I want to have a ball roll from plane A, which is above and to the left of plane B, to plane B. I want plane B to have a rigidbody. However, I don't want it to rotate too much (or the game is impossible), so I want to constrain its angle along two axes to +/- 25 degrees.

The constraints work (I use Mathf.Clamp). The problem is the ball landing on the plane first sets the x and z angles to something like -40, so on the next update the plane 'pings' up and sends my ball flying. I guess what I want to do is have plane B 'naturally' constrained and not have to update its rotation in Update/FixedUpdate - I just want it to be impossible for its rotation to lie outside these values, full stop.