Many thanks to those who have volunteered info regarding E/R skylights.
TailUK
Robert Davies
Longshanks.ghts
Re. John Lambert plans, it was his plan that gave me pause and persuaded me that there are two sets, port and starbd. What I could not ascertain were if these were raised on coamings. I believe they would have been and also sloped downwards outboard, but that is a guess. I'll probably go with this arrangement.
Sometimes they seem to be just trunks set into the deck with a mushroom vent on top.
Again, many thanks for your info.
Fortboat