I only finished when i did because i ended up screaming at the director of the company
Have you considered that might be precisely the reason why it took you so long? Losing your rag does not cut it with the Spaniards, so do not try it. Forget also all that crap about "I'm the customer", etc., as far as they're concerned they want something from you and you want something from them so it's give a little and take a little.
In my experience, the aeroplanes did not seem to suffer significantly more downtime than usual, it's just that they average something like 10 hours a day in the air every day. Just from the 50hr checks you are going to have a day downtime every week. I do agree a third twin would help things enormously, but then again, if the boss says it doesn't make financial sense... he must know better than me.
Sparx &al, there is a long running thread on Aerodynamics, which is referenced at the bottom of this one. You can find all your answers there (I'm surprised they haven't been merged yet).