Standard procedure is coving adhesive and a couple of screws up into the joists above. I went overkill and used no more nails and also fitted some reinforcing timber between the joists so I would have a wider target to screw into. Then pilot drilled and counter sunk four holes in the plaster rose. Waited for the adhesive to go off then filled the holes and caulked around the edge.
i ordered some gorilla grab adhesive in the end, haven’t seen the offending rose in person only pictures but might be able to get some screws in from the loft.
not as much weight as you have there and the flat is sold STC (not that i want to bodge it for the new owner)
Standard procedure is coving adhesive and a couple of screws up into the joists above. I went overkill and used no more nails and also fitted some reinforcing timber between the joists so I would have a wider target to screw into. Then pilot drilled and counter sunk four holes in the plaster rose. Waited for the adhesive to go off then filled the holes and caulked around the edge.