I'm glad you brought this up, since I was going to ask. There appear to be differing opinions on how to populate the houses with the figures. GD places the 1st Mother in the 10th, then goes counter-clockwise, 1st, 4th, 7th; 1st Daughter in the 11th, then 2nd, 5th, 8th; 1st Nephew/Niece in the 12th, then 3rd, 6th, 9th. Stephen Skinner follows the Golden Dawn method. I like your tweak of starting with the angular elemental house of the triplicity represented by the first figure (except it doesn't work astrologically for Caput and Cauda, which have no natural Sign/House correspondences; but see below)
In "Of Geomancy," the 1st Mother goes in the 1st house, then it goes clockwise, 10th, 7th, 4th; the Succedents go 2nd, 11th, 8th, 5th; and the Cadents are populated by combining the figures in the other triplicities (i.e. the 3rd - Gemini's natural house - is populated by geomantic addition of the figures in the 7th - Libra's house - and 11th - Aquarius' house, etc). This seems unnecessarily complex and no rationale is given for not using the Nephews/Nieces. The argument I've seen for this house progression is that the Signs and Planets move clockwise across the heavens (diurnally, that is), and the geomantic figures represent the moving Signs and Planets, not the fixed Houses. As an astrologer I can appreciate this subtlety.
The "clarification" of the GD system I found on-line follows "pseudo" Agrippa (apparently the authorship is in doubt) in the ordering of the house assignments, but uses the Nephewa/Nieces in the Cadent houses. The only oddity in all this is that the North and South Lunar Nodes don't have 'Signs" associated with them in astrology. "Agrippa" and Skinner give them to Capricorn and Scorpio, respectively.
