Although it is not a superior functionality, it can be used with confidence. I use it by stacking up to 4 stages but it is stable and no problem.
As a hope, it is more convenient to hold back the rattles by slightly narrowing the slit width (it is necessary to limit the thickness of the slide glass).
Also, it is preferable to prepare variations of the same external size and large pitch (thus reducing the number of storage), or conversely reduce it to widen the degree of freedom of the interval. I think that it is better to not change the external dimensions because I think that there are many users already stacked up.