I've done it on all bikes. In my view 06 FZ6 has just the right gearing. If you go down - will be too short, go up - too tall. Personally I don't really care in what gear I am as long as I'm in the RPM range which gives me enough pickup and torque. I think the 6th gear in an overdrive. I often ride in 5th on a highways at about 70-75 mph, and move up to 6th when there's an open road ahead so I can just cruise and relax.
You also can install an aftermarket gear indicator which will be 90% accurate.
When on the freeway, I find myself reaching for 7th all the time. It was even worse on my vStar, as that was only a 5-speed. But I also now have an Aprilia Tuono and I've never even had it in 6th gear. At 70mph in 5th I'm turning less than 5K RPMs.