Bitsavers just posted the DeclROM dump and PCB photos for a full-size Duo Dock. The DeclROM parses well with the Hex Fiend extension. @joevt's SlotsParse works but claims the CRC mismatches and should be 00000000, which seems like a possible bug. It's about the only DeclROM I've seen that has a byteLanes value of 0x0F (0,1,2,3), which may be related.