Ceiling Cladding Advice Please

[WotEver]

1 hour ago, Boater Sam said:

Thinner than 8mm T&G would be difficult to secret pin to the battens, it splits the tongues off for fun. 5 minute Polyurethane wood gel and prop it all?

And you’d have to machine it yourself I think. I can’t imagine even B&Q selling matchboard that thin.