Hi, I'm having the same issue.

Using the Virtual Scene Scale Factor does work on image targets ( scaling them up and down ), but does not scale the Ground Plane Stage ( same thing for Mid Air Stage )

Go to Window > Vuforia Configuration and then change "Virtual Scene Scale Factor".  Does that work for you?

They developed an AR engine with all unreacheable scret stuffs. Why do not people prepare a good documentation? Why?

Hello Vuforia Team

Is there a providen solution to scale up the ground place grid ?

When I place my objects on the Ground Place Stage, they are ridiculously small with a very low shadow resolution.

Sunnychao here seems to have found a solution, but it seems to me a bit complicated and I would prefer use something build-in your SDK.

I got it to work. Follow my comments and it should get you there. 

https://forum.unity.com/threads/best-practice-for-scaling-placed-objects-with-new-ground-plane-markerless-tracking.513344/

This guy figured it out. I'm trying to get it working on my project but no luck. If you guys can figure it out, I would appreciate you letting me know what I did wrong. I posted all the steps I took. We should spam this forum about this issue so they can see that this is a big issue.

Same problem here.

I have a room model that I made 'Desktop' size so it can be viewed using the Vuforia ground plane on an office desk. The problem is when I scale the model down to a size that fits the ground plane, the shadow resolution is appalling, so what I want to do is keep the room model full-scale and scale up the ground plane gameobject......except I can't!