Plate perpendicular to bottom of square brick/plate: is this connection legal?

Question

This is closely related to the question about jamming plates underneath 2x2 round bricks, (and indeed prompted by a comment there), with differences explained later.

It is possible to attach a plate (or tile) to the underside of a square rectangular brick/plate/tile, between the wall and the tubes, like so:

Note how the distance between a brick's wall and its inner tube seems to be the same as the thickness of a plate:

A few observations:

• This connection feels looser (seems to have less clutch) than using a round brick.

• For 1-stud-wide plates, this connection doesn't guarantee a straight angle. The edge of the plate sits loose inside the brick.

• For post-2005 regular bricks (i.e. non-sloped), since they have thinned walls with notches at every stud, the connection is particularly flimsy. A 1-stud-wide plate just won't get any grip at all.

• The walls of rectangular bricks are connected to each other, so bending a wall "outwards" (to jam a plate/tile inside) means bending or stressing the perpendicular walls (as far as I understand the physics of solid materials).

So:

• Is this connection "legal"? (i.e.: Does this connection stress the parts involved?)

• Has this type of connection been used in any official sets?

Answer 1

To answer your second question: The technique was used by Lego in 1976's set 726 (12v Western train with 2 Wagons and Cowboys), to attach the horse's tail.

See page 13 of the instructions:

Answer 2

Some anecdotal evidence against legality: I have built such connections with rather old plates a long time ago and one of the outer plates failed (the wall breaking off). So it certainly puts the plates under some stress.