Stacking fridge and freezer

I have stacked my fridge above my freezer.

No kit, just feet of fridge on the top of the freezer!

Have I committed some cardinal sin?

Only if it's a chest freezer.

The weight of the fridge will distort the chassis of the freezer. Eventually the door of the freezer will not close correctly.

For units which permit it, a coupling kit is needed to prevent the top unit falling on top of anyone who pulls on the open door. Sometimes includes a seal to prevent air circulating in the gap inbetween, where it can cause condensation to form a puddle.

No doubt wise if you have small children or infirm relatives, but it takes a fair pull to tip the one I have on top of a freezer. (It is a fairly old and therefore heavy fridge, but the weight is well biassed towards the bottom).

I guess that would be dependent on the freezer.

So far my fridge has been on top of my freezer for over 3 years.

When do you think I should anticipate any problems of doors not closing properly?