Thanks for the feedback guys. It’s good to have a record of what actually worked.
I’ve just had a play with my friend’s DS210j, which is pretty ancient and runs DSM 5.2 but seemed to work just fine on the tests that I threw at it. I’ll write up my findings in a day or two.
Correction: It was DSM 5.2, not 5.1
Edit 2: Write-up is here.