French balcony - installation directly on the window frame - experiences?

Hello everyone,

maybe one of you can help me and has already dealt with similar considerations.
We have two floor-to-ceiling windows on the upper floor that still need to be secured with a French balcony.
Preferably with safety glass.
The window reveal is quite narrow, so mounting in it is not possible.

The "balcony guy" has now suggested screwing a corresponding profile directly onto the window frame.
Also possible with plastic windows, since the frames have a steel core.

We really like the look,
I just have a few concerns regarding sealing, both concerning moisture and heat.
After all, holes are being drilled into the frame...

Can anyone share any experiences?
Has anyone solved it like this?
Had any problems with it?

Thanks and regards

maybe one of you can help me and has already gone through similar considerations.
We have two floor-to-ceiling windows on the upper floor that still need to be secured by a French balcony.

We have already discussed this topic several times - thanks to the search function it is hard to find - most recently here:

Thank you for the link. But it's more about the fundamental question "Whether or Not" there. That has been decided for us. Something has to come before that. My question was more about the system (installation directly on the frame). I also wouldn't know exactly what to look for......"French balcony" unfortunately didn't help me further

Anyone else have an idea on the topic?