Your observations and comments Steve are absolutely correct, those system 6 were the first effort made by BMW to make a helmet at their new design and manufacture facilities, afraid they did so with an unsatisfactory result.
They claim that new design had improved all aspects, still I'm not convinced.
System 5 is superb both in peripheral vision and its silent less, downside the lack of a dark visor that 6 has but with a good pair of sun glasses this can be eliminated, ventilation is not so good just adequate, and intercom is perfect. My misses and I love them after 7 years we keep them in good order, two times for each one had to change batteries, found for 5 euros in the net.
5's among with the Sport tricolor helmet and the fisrst open helmets for scooters, were the last products made by Schuberth for BMW, that partnership ended in 2011.
About intercom my Inter phone 4 system is really started to produce almost daily issues especially with connection, something the new pair of cables have not cured, so as a second daily set I'm thinking to follow the road towards Scala too.