I dont think you will have much luck finding longer extensions for that boom. 45cm is pretty much as long as you can get otherwise the extension can foul on the curve of the boom and it weakens the boom too much- the rear of the boom is the least stiffest part so it puts more load on the stiff front section of the boom which will lead to failure.

I would buy new since they arent that expensive but I guess that is a relative thing on how much you sail. You can also buy secondhand but be sure to check the head of the boom has no cracks and there are no signs of corrosion- "bubbles" under the grip is probably the worst sign. Generally good brands to look for secondhand are North or Chinook. Alloy booms have a limited number of cycles so by keeping your current (if it is old) might be putting off the inevitable and sailing back with a broken boom aint fun. New booms also have simple head clamp systems and a better pin system at the rear so they are often easier to setup than the old booms.

My suggestion is to go speak to Simon at Board Crazy, he will help you out and the stuff he stocks is good quality

Thanks guys, looks like I might rethink things - I have 2xsails that fit the original boom, and both sails have batons, the general shape being that of sweepeing up from the bottom, and jutting out a bit at the top, sort of like the nore modern sails. However, all this weight up top is a bit heavy for my little bro, so I picked up three sails at the market, for $5 each. The one with the 2.5 boom is very traditionally shaped, that is like a triangle with much less square area but a longer and lower boom length, does this make sense? (OLD)It also has a sleeve for the top metre - no sail, so I'm guessing its a beginners sail. I'm unable to cough up much for a $5 sail!! I will keep a look out for an old boom to suit rather than weakening the current one. Cheers

$5 no great loss, they make good decorations hanging from the roof of your patio . What size sails have you actually got (it will generally say near the bottom of the sail or maybe on the bag).