Sure, after trying a North Platinum and a Nautix Jumbo (supposedly very stiff as well) it's pretty obvious that the rig feels more nervous with the carbon boom. Now is the flex such a bad thing, as long as it doesn't affect the profile of the sail too much? You may appreciate it after long hours/long distances. Masts of various carbon content have the same static flex but different dynamics. Is it the same for booms (i.e. combination of static/dynamic flex)?
PS: the NXtrem tested in German Surf Magazine is the regular alu version, not the hybrid one. That's why it sits between the NS Silver and NP X3. I wonder why Nautix discontinued the hybrid version. Will ask them at the next Salon Nautique.