Hi!
I have a similar problem.
I started to develop for the Focus Plus a week ago.
Reading your conversation helped me already, since I added the "CustomDeviceHeight" Script into my sence (to the ViveRig object) to adjust the INITIAL deveice height. So when I start the scene everything is fine.
But still, everytime I use the teleport function (ViveInputUtility script), the height messes up and I am way too high in the virtual world (about 1 meter too high).
I followed all the instructions given here (order when to put on HMD...)
I have the problem that I am unable to pick up items from the ground, since I touch the real floor before my controller in the virtual world touches its ground.
Id be very very thankful for some advice, since I am looking for a solution for multiple days already.
Cheers,
Magnus