Something I'll try if necessary-
Shift to the big ring.
Turn low limit screw in an extra turn or 2. (varies depending on "how short" your FDER is from making it to the big ring)
Shift back to small ring.
Reattach cable pulling all slack out. You might want to give the barrel adjuster a turns worth of leeway in case you get the cable too tight.
Back off low limit screw until you get a reliable downshift.