Rule 4

PE19/65 ft.

Strong secondary accent fell on initial or long syllable separated by one or more shorts from stress.

PE19/60

The secondary accent falling on the initial syllable, or any non-initial long syllable, that was separated (by an intervening stressless long or one or more stressless short) from the main was strong.

RGEO/61

In the very frequent cases of words ending in two short syllables, [...] they received a light stress that could be used metrically.