Further to my mention of Krazy Karpet scraps, I did this a couple of years ago.
Very good solution, I met an audax rider who have a block of wood neatly cut and trim to increase the gap between the back of the bag to the seatpost.
Not pretty but a lots lighter.
@edscoble started
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Further to my mention of Krazy Karpet scraps, I did this a couple of years ago.