Thats what I fly, 65kt normal approach, and those other speeds are what I have been using. I'm glad I'm not the only one to think that 80 sounded fast!
I think the rule of thumb you use znww5 is what my instructor said...half the difference added on. I guess the reason for this is to add a buffer zone yes? Then again, I thought that the reason the approach speed was the approach speed was becuase it was the most effective+a buffer.
This is why I was wondering why you would add a factor for gusts, as I figured the approach speed already had a factor inbuilt.