For the fork, I'm using the Surly Pacer (I wasn't planning on building one... maybe that's an option). 45mm rake for 57mm trail, 371mm axle-to-crown.

There's a little overlap with tire radius at 28mm, but I plan on running 23mm. I could stretch out the TT to 520-530 (I noticed many commercial frames go about this), and just use a shorter stem? That would buy me about 1-2 degrees, I think.

The standover is about as high as I want - with shoes and 23mm tires, about 1" clearance. I tried making the ST shorter (I think I'm nominally a 48), but then the TT and DT overlap on the HT. Ugh.

If I built a fork, perhaps I could minimize the tire clearance, thus extending the HT downwards, and opening up that angle?

Thanks for your story about your experience modifying the ST/DT angle. I'm definitely leaning towards not doing that. Small frame compromises indeed!