By comparison, this is how an all-aluminum boom (North Silver) is flexing under load while windsurfing in real life :
http://www.youtube.com/watch?v=JcEP0cJjrEA
The boom is way softer all over the arm tubes (especially when pumping the sail) than a carbon boom. Pretty obvious about how an all-carbon and an all-aluminum boom do flex in real life as compared to lab test results...
Cheers !
JM