RE: Roger, should I go for carbon?
Very interesting question!
If you live where there are alot of sailors, or WS shops, I'd look around for a good carbon race boom as this should provide you with the best long term performance.
If your local racers are "breaking" alu. booms in one season, I'd check to see what the failure mode is for the booms that have broken.
Be sure to look for a boom that's significantly longer than you need.
For a 246 cm nominal recommended boom length, I'd think you need a boom that when fully extended goes out to around 260-270 cm.
The Chinook is good, just be careful with the "triple clamp" and not get it too tight as the triple clamp has a bit of a reputation for having a little "too much" leverage, which can allow you to "crush" your mast.
The Fiberspar is pretty good also, but you may need to get a kit to repair the back end if it has the locking ring setup. Be sure to check the used boom to ensure that the locking rings and collars are in good shape.
Hope this helps,