Your quilting so far is very geometric and not fluid and organic like feathers. I would most definitely not put feathers in the border. If this were mine I would treat all 3 strips like a single border unit. In fact I would be sorely tempted to turn the design you used in the setting triangles into squares on point and continue the exact same quilting you have done in those down into the border. Sorry for the bad computer drawing skills but something like this:
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