Vitamin D requirements, time in the sun, and dosage to eliminate deficiency

Dr Holick's table of recommended dosage.  Based on info in Holick's and other related books (and my current blood level of Vitamin D of around 18.8 ng/ml, and weight), I've decided to take 5000-6000 IU of Vitamin D each day. I've ordered high strength Vitamin D from here.

Key tables are provided below.

Based on my skin colour I'd generally need over 40 minutes in HOT SCORCHING SUN in summer to make my daily Vitamin D. That's going to be hard to do, so I'm going to have to take supplements on an ongoing basis.

Holick's barometer (p.45 of his book)

Key tables:

p. 46,49, Dowd:

From p.143, Zaidi:

Holick p.204: calcium