Any question answered...

Situation is as follows:

• Paragon Machineworks dropout
  
• 11 speed wheel (Tested with both HED Stinger 4 and a FLO30 running a Chorus cassette)
  
• 9070 rear mech
  
  

The dropout is 4.5mm thick - which precisely meets the Shimano tech requirements.

The way in which one adjusts a Di2 rear mech is to shift to the fifth sprocket from the largest, then use the micro-adjust to shift toward the 4th until the chain starts to chatter.

You then back off four stops which puts the mech in the correct place.

But I can't- I can back off by 1, so the chain doesn't chatter, and I get decent shifting, but it's not "to spec", and it's driving me nuts.

So I want to space the rear mech out by 0.5mm just to get that adjustment, and a shim washer with an ID of 10mm and OD of 12mm seems the thing to use.

The dropout is in the right place, and is commonly used for Di2 bikes, so I don't know what's going on here -maybe my mech is a duffer?

Sounds like an 0.6mm chainring spacer will do the trick, certainly worth a try.