Help With Boundary Points from Plane

Greetings,

I want to create a Level at runtime which depends on the given real conditions/enviroment. Therefore I want to use the Boundary Points from a selected Plane, so I can create a grid onto that plane. For the Scaling I use the information from this post (https://forum.unity.com/threads/scaling-with-arfoundation.543953/).

The Problem is, if I place a Sphere on every Boundary Point, they are not where I would expect them to be, if I rotate or scale the scene. The spheres also scale, wich I do not wish, as they are no longer on the edge of the plane.

I hope anyone has a Idea how i can use the Boundary Points or get Random Points on the Plane or how I can create a grid level at runtime.

i use:

ARFoundation : 3.0.1
ARCore: 3.0.1.
at the mom only i use Android

cheers Dex