Flying hotspot oy

Hi,

I'm pretty new to krpano and I'm trying to make a UI using only hotspots, because I need popups in VR Mode.
Ideally I would like to do everything in hotspots, so I don't have to rewrite things with layers when we are out of vrmode.
All is going great, except today that I'm testing things on mobile devices.

I was going from this example : https://krpano.com/releases/1.20.…ut-hotspots.xml
Key configurations for hotspots to achieve this is :
- flying = 1 : so the hotspot follow the view
- scaleflying = true : so out of vr mode, screen height is managed as it is 1000px
- distorted = true : so scaleflying is working

I have this hotspot definitions, to show a big red square that takes half of screen height, and a little blue square, wich I want to positionnate on top edge of red square

<hotspot name="bg"
       type="text"
       width="500"
       height="500"
       bgcolor="0xFF0000"
       flying="1"
       distorted="true"
       keep="true"
       zorder="0"
/><hotspot name="close"       type="text"
       enabled="true"
       width="20"
       height="20"
       distorted="true"
       oy="-250"
       flying="1"
       bgcolor="0x0000FF"
       keep="true"
       zorder="0"
/>

Here is the result in an iphone12 :

And the result in a galaxy S8 :

As we can see, the oy parameter of blue square isn't taken by the effect of scaleflying, while red square height is, otherwise blue square should be perfectly on top border of the red square.
So I have a question : how can I do that ?
I have seen that deactivate scaleflying makes things working ( that's what I do in vr mode ) , but in that case I don't have the good scale depending of my screen height, maybe it's a matter of fov, but I don't know wich formula I could use to achieve this.

Thanks by advance !

Ho thanks :)