Roof - continue slope downward puzzle

[dstig1]

The continue slope downward checkbox seems to be the tool for this job, but is not working as expected. I want the roof plane to be continuous across this wall from the covered deck on the left on through past the wall on the left. I only want one roof plane for this. I have checked "continue slope downward" for the circled wall and made the 2 abutting walls full gable as required. Is it not working because the one wall is a deck railing, or is there something else I am missing?

I have also tried making the wall back from the deck into full gable but that had no effect. I suspect I could fool Chief by just temporarily extending the main wall until after roof planes are built, but haven't tried that yet. It's late...

Any clues?

Thanks,