Traveller Mk 3 - overload on pre inputs

[randallp]

I purchased a Traveler mk3 and hooked it to a Mackie Onyx 2480 using channel direct outs. I was unable to get the T3 to pad the pre-amped inputs low enough to avoid red light signal strengths. (I of course first set the Onyx to 0db using it's pre gains) The analog line-in inputs were fine.
I read about and tried using the pad (held knob in until a click and PAD lit up in the display) but it didn't seem to make much (if any) difference.
Am I missing something or is it not possible to use the 4 x pre inputs for the direct outs from the mixer?
If I reduce the mixer channel gains low enough that the T3 isn't overloaded (by -20db) then there is not enough volume coming to drive the PA (I only get one green LED segment of the Mackie channel meter to flash)
Edit: 3/13 more info - the direct outs are 300ohms - is this not a good match to the T3?