Sievers' Law in Germanic/Old English

I read that Sievers' Law in Germanic/Old English applies not
only after a heavy syllable but also after two light
syllables, but not after one heavy + one light syllable, so that
if I understand correctly we have not only

j > ij / VCC _ V
V:C _ V

but also

j > ij / VCVC _ V

but *not*

j > ij / VCCVC _ V
V:CVC _ V

Have I understood this right, and if so why is a sequnence
of two light syllables counted as heavy, but a sequence of
one heavy and one light syllable not counted as super heavy?
I guess it has to do with rythm somehow. I suppose the
stress (PIE or Germanic?) must fall on the first of the two
light syllables.

This obviously has its repercussions on West Germanic
gemination, but are there examples of this from other
WG languages than Old English?

Also, does this syllabification after two light syllables
happen in Scandinavian too?

--
/BP 8^)>
--
Benct Philip Jonsson -- melroch at melroch dot se

"Maybe" is a strange word. When mum or dad says it
it means "yes", but when my big brothers say it it
means "no"!

(Philip Jonsson jr, age 7)