The life rings.
I found some plastic ones on eBay that were roughly the same diameter for a couple of pounds each that looked ideal.
The rope detail needed to be added to them to replicate the originals and this was done with some nylon cord that I superglued into slots filed into the circumference. I then wound seven turns to form the quadrants, securing each turn with a spot of glue and ensuring that the ends all arrived on what will be the underside of the rings.
They were then sprayed with a couple of coats of white acrylic and the red bands brush painted.
The weight of the new life ring is 19 grams, exactly one third of the metal one and it looks, to my eye, a million times better 😁
To locate them on the engine room roof I cut some 3mm plasticard wedges and superglued them in place, the actual fixing will be two small screws from the underside of the roof.
The white metal ones will make ideal ballast weights if I need to make any adjustments 😉