Terminator,
Thanks very much for your explain - much appreciated.
The only thing I'm still a little unsure of is regarding the speed tape black & amber bands. If the low speed envelope limit doesn't change for IAS (or CAS), why does the lower black & amber limit increase with altitude (see link below), bearing in mind the speed tape is showing IAS/CAS?
Boeing 737-8K2 - Large Preview - AirTeamImages.com
Thanks very much.