I would suggest at least a 5wt 9' even a 6wt9'.Something else you might want to consider is going with a few extra spools with different line.If the wind picks up throw a 6 or 7wt line if its calm you can go with a 4wt.I fish the bitteroot every summer and the wind can get howlin at times through the valley.And if so the heavier line really helps.I have a 9' 5wt orvis and it handles a 7wt line in the wind just fine.I leave my 4wt loomis at home.TM
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If ya can't run with the big dogs stay on the porch!