I’m planning to add a flanged shower draw off to a vented hot water cylinder…

As always with an older house, there’s always a complication. The cylinder is close to the ceiling, so I need to minimise the stack height (or cut a hole in the ceiling).

Would I be right in thinking that a 1970s era copper cylinder is likely to be a 1″ female BSP outlet for the hot / vent outlet???

If so, the flange I have will fit – but I then need to go from 1″ female into a 22mm horizontal T…
I know I can go 1″ BSP to 22mm compression and then onto a 22mm equal T.

Is it best to do this as 1″ BSP:22mm compression onto a 22mm compression T, or can I go from the adapter onto a soldered T…? (I’m thinking that the second option might save on stack height)