Here's one of Greer's latest offerings. Seems like a simplified OCD circuit with some value changes and different clipping diodes. Schematic for reference. Easy fit in a 1590B.
This is a library of perfboard and single-sided PCB effect layouts for guitar and bass. I'm not an electrical engineer by any stretch of the imagination, just a DIY'er who likes drawing layouts. It is meant for the hobbyist (so commercial use of any of these layout is not allowed without permission) and as a way to give back to the online DIY community.