I started LF photography with a Luna Pro F, added the 7.5/15 ° attachment, bought an Ultra Spot, sold the Luna pro and spot attachment and never looked back.
I had to look up the Ranger 9, nice meter. It has an 18° angle of view. Maybe make a 18° wedge to put next to the sensor so that you get a better idea of the area being read. Its really not amazing what a .5° shift in metering position can do for the reading.
It's got a sight window, on the face side, it has a circle in it. On the back side, when you put your eye up to it, you see a frosted smaller circle, therefore you can aim quite accurately.
Ralph.. Don't really understand what you are specifically referring to when you state ...
you might be photographing on the wrong day if the Zone System cannot help you to manage the contrast.
where located here in the sunny southwest, northern Arizona.. usually shoot Zone 7.
Ate lunch, now time to do 'Darkroom 101',
and do the development ... 12 shots.. some @ 400 some @ 200, bracketed, and used yellow and orange filter, on both... incident reading and direct.. but no neutral density as the horizon was broken up.