Wish I could help but I have up on the 3 1/2" shells years ago. My fillings were taking a beating lol. But I would say if you are going from 3" to 3 1/2" you should be good since you have a 1/4 ounce more shot. But I would still pattern since I am an anal retentive type person. I would say just fire one shell at 40 yards and make any minor adjustments
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