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.