v3d-container not filling parent div after appendChild????

Hi Verge’rs
I was experimenting with my new made template I wanna use for future projects…
It’s has scalable menu’s and detects screen aspect ratio’s.
I first set it up in pure html and it did what I wanted it to do.
We had some issues with the requestFullscreen() on Ipad (it snaps outta it on text input for some reason)….
So I made a ‘fullscreen’ function which is more like a body fullscreen.
It loads my ‘ConfiguratorHolder'(= menus + v3d-container) into a div and hides the scrollbar etc etc. It works pretty well,……The problem is: when I appendChild the configuratorHolder, the v3d-container doesn’t seem to fill out the space(red)
When I resize the window it snaps back to fill the parent div,(see My-Recording_Trim.mp4 )
Anyone any Idea’s how to fix improve this???
Any help would be much apricated!!!

ProjectLink:
https://cdn.soft8soft.com/AROAJSY2GOEHMOFUVPIOE:95a3606e33/applications/my_awesome_Cube4Ronald/indexcvk4.html