Have the same sail and use my formula boom X9 225-275 - but thatīs a big boom for this sail :-( Such a big sail really needs a carbon boom (some people say)..... So if you are a milionare you can buy the new X9 200-260.
I think you are right about you boom/sail combination - it will eventually bend or break....
Maybe you can find a cheap 2009 X3 225-275 boom - the old red ones are on sale most places. Then you donīt have to extend it som much and it will be stronger.