My bike parts arrived, including the Sugino-specific Blackspire Ring God. This is not a weight-weanie part, just begs to be beat against pine and granite. The 25t Endless cog is enormous, we’ll see how 7075 alloy wears compared to stainless steel.
Update: the guard fits beautifully, and everything else went fine. The shifting is funny, and I’ve put up the project for the evening at that. The Endless teeth may be too tall to function properly in this way, necessitating a grinder. The Surly ring has a hiccup periodically that doesn’t make any sense to me. I’ve yet to compare tooth profiles to conventional cogs out of a cassette, therein may lie my answer.