OK, so I can confirm that some racks do NOT fit Royals nicely. The reds, in particular, are thicker and don't fit 20-to-barrel. That's what happened with my generic 43mm racks.
- Bud Jones racks from Apache fit them PERFECTLY
- Matsui racks fit them great, so if a birdcage is in your future, go with that as other racks don't fit in birdcages