Scale is not working in Unity.
Unity 5.4.2p4;
Houdini FX 15.0.416;

Copy stamping will not work in Unity because it breaks instancing. Instancing requires all meshes to be the same but copy stamping actually makes each instance unique.

To scale instances, you need to use the pscale point attribute. For an example use of pscale, see: https://www.sidefx.com/tutorials/painting-color-and-instance-scale-unity/ [sidefx.com]

Thank you for the video,
pscale- not work in Unity for Instance, need
scale-(float3) this attribute will be to translate the scale.

I corrected file

My bad. Yes, scale is the one you want for instances.