ᐅ Attic conversion using OSB boards and vapor barrier

Hello,
I started building over a year ago, and we have since moved in.
The upper floor was finished with roof battens, drywall panels, a vapor barrier, and insulation installed above it, all inspected and approved by a building inspector. The insulation and tests underneath still show positive results; everything remains completely dry.
Now, I want to screw OSB panels, which have been stored in the attic for about a year, onto the joists above the insulation.
However, I am a bit uncertain about the risk of mold growth. Everything is currently dry, and the vapor barrier is properly installed.
A wood moisture meter showed that the OSB panels have a moisture content of 5-10%, which the device indicates is low.
Still, I am concerned about mold.
Should this installation work, considering the panels are unlikely to ever be 100% dry, and any moisture would—if at all—rise upwards? I plan to leave about 2-3 cm (1 inch) of space around the edges to allow the panels to expand. However, this would mean the installation is not completely airtight.

Is this approach safe?

The description of the construction sounds odd. So, from the inside to the outside, you have the following layers:

Insulation (how thick?)
Vapor retarder
Gypsum board

@Dr Hix He means the ceiling, so you have to think from bottom to top.
@TheKMKM You can safely install the OSB boards there, the structure is suitable. It will never be 100% dry, and that wouldn’t be ideal either.

Okay, that could of course be the case, the term "roof battens" confused me.

When it comes to the top floor ceiling, I would make sure that the OSB boards are not laid completely airtight over the entire surface, otherwise you create an airtight sandwich from which any moisture that gets in cannot escape. You really don’t need to worry about the residual moisture of the boards (or of the structural timber used) in this regard; it’s more about leaks in the vapor barrier, which almost always occur during installation.

So, leave about 20cm (8 inches) or more free at the edges, and ideally also include small gaps between the boards. Some people alternatively drill holes in the boards. There should be air circulation possible in every single rafter cavity below the OSB.

Wood is considered dry at 20% moisture content or less...
So you can install it without any worries.

Thank you, the answers have already helped me a lot!
One more question though. If I leave space on the outside and the attic is not completely sealed, can moisture still get under the OSB panels in the summer?