I'm using Hp5, at Ei 200
I'm also using a sekonic 758D.
I'm using a Metz 58-af1 flash gun

Situation / objective / previsualization:
the sun is behind to the left, and is being used as a hair light
a flash is in the fron to the right, and is being used as a fill light.
My objective is trying to render the background (sky + clouds) darker than the subject. (i.e. portrait)

My process + problem:
Metered the sky (using a reflective spot meter) and added two stops to render the background nice, dark and moody (the way I wanted)
(example: meter read f/11 1/250 --> I dialed in f/22 at 1/250)
THe problem, i'm not sure how to dial in my flashgun to get the correct exposure for hte subject

solution #1
used the guide numbers, to dial in the exposure.
(example (at power: 1/-1/3, distance is 1.9 meters (which is the distance from teh subject)))
problem #2: is when i then change my meter to reflective it is reading a very weird value: (i.e. 1/250 f/5.6). Which is a far cry what I have already dialed into my flash gun.

Do I trust my guide numbers or my meter? Shouldn't they match?