John Rumm wrote:
Owain wrote:

Battening might strain the plaster to cracking. Perhaps loosly fitting


It might, but would you care if you are going to PB over it anyway?

plywood under the ceiling, then acropropping it up to push the laths


This technique can work for reparing a L&P ceiling - push it back
temporarily and then pour extra bonding plaster on top to stabilise it...

Something odd about the attributions here.... however, WRT repairing
P&L ceilings, if the nails have let go (rust or pull-out) this is a
not recommended repair.