Start pure X11 with fullscreen remote-viewer to started KVM instance

Question

Intention is to start LightDM session with only VM and connecting app working, so no other apps will interfere with its usage. I've created .xsession which starts KVM domain and remote-viewer in fullscreen mode.
KVM content are two displays with resolution matching my OS resolution.
Problem is that remote-viewer starts with top-bar visible moving content those X pixel to below bottom edge. When I manually move remote-viewer windows by those X pixels up - then it looks acceptable.

#!/bin/bash
#start VM machine
sudo virsh start debian_vm_1

while true
do 
  [[ `pgrep kvm | wc -l` -ne 0 ]] && break; 
  sleep 0.5s;
done
xrandr --output DP-1-8 --primary --right-of DP-1-1-8 --output eDP-1 --right-of DP-1-8
remote-viewer --auto-resize never -k --kiosk-quit on-disconnect spice://localhost:5900

As you see - trigger to close session is closing viewer.

• how to make remote-viewer hide top-bar? setting fullscreen works in i3 WM (top-bar hides nicely), but in pure X11 doesn't
• how to move 'remote-viewer' in a delayed way?

PS: As a workaround I could start i3 with default profile and use it to handle windows positioning.