I thought that, which is why i changed the feature code to only be the number 6. That reduced the string length to 6 digits with a 4 digit station group. and that still didn't work. 6 digit with a 3 digit station group works as does 5 digit with a 3 digit station group.

I am just using the default dailing plan on the GS phones which allows full lcr +10 and 11 digit dialing so total length isn't an issue. I can directly dial a 4 digit station group or extension so that seems to be fine.