Hi Dave,
You do like a challenge.
I had one of those and it had a short lifespan. I replaced it with a repro Desmo type with the screw back suction device which has the Morgan Wings on the central back screw. I bought it on e bay from a dealer called 'Jags of Bursledon' for £9 + P&P who specialises in them for all marques.
With mine, you have to screw it up fully to see where the Morgan logo end up and then turn the whole thing so that it is level when tightened next time. simples yes.
