Placing loose plasterboards

[LeeUK]

I am currently insulating and boarding between beams, the boards are 500mm wide x 2500mm resting on 14mm wide x21mm battens.
This morning I woke up with my mind telling me they'll sag and fall out !
Plasterboards are 13mm

Can anyone put my mind at ease

 

[Deluks]

Even if they do, you can just pop a few horizontal battens in and put them back.
If there's excessive moisture in the air then they might absorb it, then they might start to sag in the middle.
But It will most likely be fine as it is.