BVH depth and recommended stack depth

In most examples, a `SmallStack` with stack depth 64 is used. If I understand the code correctly, you can run into undefined behaviour (in Release mode) or generally issues if your `SmallStack` is too small. Is 64 so large that there will never be a case that it's not enough? Or would it make sense to use `GrowingStack` and call `reserve` on the elems vector beforehand to make sure it's fast enough? Is there any out of the box way to find the BVH depth? I couldn't find one and it doesn't seem like it's tracked during construction.