The rule is a safelight should always be off when using an analyzer.

An analyzer is going to be much more sensitive then a human eye.

IIRC Paul Butzi's website on dichro heads he arrived at the numbers from testing his enlarger and paper. It's possible your enlarger is a little different then the standard. Maybe the filters have faded a touch? Who knows.

I don't know about your analyzer but the one I use for colour requres a special probe for VC paper grades. Considering the price for the probe I'll pass-)

Dual filtration is great if you're changing grades alot in a production enviroment. Even greater if you don't have an analyzer. If you're analzyer can handle VC then I don't see why you'd want or care about dual filteration. Just dial in the filter and let the analzyer set the time. But then I spilt filter without an analyzer.

You might want to take the time to do a VC paper test. It'll require a step wedge. Afterwards you'll know what settings on your enlarger produces what grades.