If tip diameter won't yield you 8X8's and you already have enough rafter stock, you might consider going to 7X7's in your gable bents. They are carrying less load than the posts in the inboard bents and in that you are not joining pieces from both sides the smaller section does not compromise joinery.
If you havn't already planned on it, milling your brace stock FOHC is a worthy end use for these butts.
A little wane never hurts either !
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