I've forgotten which way up the big failsafe washers go.
I think they should have the dished side facing downwards, like an overturned saucer. Like so:
Putting them on the other way (dished side up) would be bonkers 'cos they'll just fill up with water.
Rimmers diagram looks like dished side down but it's not clear enough to be 100% certain.
https://rimmerbros.com/Item--i-GRID001554
Can someone confirm dished side down please (or otherwise). Ta in advance.