As often happens, every idea stems from a need: I needed to stack two polydryer boxes while using the dryer in the upper one. 

I found it interesting to use the same system used by the Airlock Stacker model provided by Polymaker.

I recommend printing with PETG to prevent distortion due to heat.

Unfortunately, the new design requires some supports, but I have tried to limit their use as much as possible.

 I had no problems using them and the finish is still quite good. If you have any other ideas on how to reduce the supports, please let me know.