Keep scale uniform with Stretch To constraint.

In Stretch To constrain, there is an option to keep the volume of the object. Is it possible to do the inverse — keep relative scales, i. e. to maintain object shape? Maybe with another constraint.

​Are you trying to use Stretch to constraint to scale the mesh?

I’m doing something like 2-point tracking. There are 2 tracks with empties aligned to them. I want to “pin” some plane with texture by these empties, so that it translates, rotates and uniformly scales (all in 2 dimensions) such that they keep their position relative to it, but does not deform otherwise.

I try to achieve this by making the first empty Stretch To the second empty, and making the plane a child of the first empty. The plane scales as desired along the first empty’s Y axis, (which points to the second empty because of Stretch To), but what I want is to scale its other axis by the same amount.

So in essence yes, I’m trying to use Stretch To to rotate an obect towards another object, and scale it proportionally to the distance. Is there a better way?

Still I would like to know if there’s a simplier way to do this.
In Edit mode, when bone end is dragged the bone adjusts its size uniformly, without deforming. Maybe there’s a way to make the bone end permanently snap to an obect, other than Stretch To constraint, which deforms the bone?