You should put an eyelet on the back of the Seat tube to attach the mudguard
Edit: looks like you did already?
Why?
It's something Daniel Salmon used to do on bikes with closer clearances. Supports the mudguard without the need for a bridge between the chainstays.
@Hulsroy started
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You should put an eyelet on the back of the Seat tube to attach the mudguard
Edit: looks like you did already?