Hello Spaehling,
Indeed, non-power of two resolutions are currently not supported by the Substance engine. We are aware of the interest in this feature and its usefulness, but have no plans to share at this time.
In the meantime, if you feel comfortable with this you may set up an automation pipeline involving a separate tool that crops images exported from Designer or SBSRender – which is included in Designer's installation – to the correct format. I appreciate your patience!
Best regards
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