Thanks for the response.
The camera is destined for a correctional facility cell... so shims would need to follow the contours of the existing housing precisely which means complex curves. That means an expensive solution to an already expensive camera
The housing is designed to be anti-grip, anti-ligature, and can easily be sealed against the mounting surfaces with anti-pick sealant to prevent ...persons... hiding stuff like credit cards/razor blades etc in the gaps.