Yes, 9 and 10 spd front mechs have the same pull ratio I think.
I've certainly not had a problem mixing them.
Sounds like something's wrong with the cable tension at the front.
The spring in the front mech is very strong, and you need to clamp the cable up well.
It's possible the cable is no longer seated correctly inside the shifter.
I'd be inclined to set it up again from scratch.
Here's how I do it...
Un-clamp the cable from the mech.
It should fall back to the granny ring.
Adjust the limit screw if necessary to allow it to properly sit over the granny ring.
Ensure the shifter has let out all the cable it can, by operating the inner paddle whilst pulling on the cable at the down-tube.
Sometimes, the nipple at the end of the cable has not seated correctly in the rotating drum inside the shifter.
Inspect it, and whilst maintaining firm hand-tension on the cable, check the shifter can operate up and down.
Be sure to leave it with the most slack cable paid out.
There is a small plastic wedge that comes with the mech, which holds it in a partially-activated position ( ie not fully relaxed onto the granny ).
With this wedge in place, pull the cable firmly by hand into the clamp on the mech, and nip up the clamp bolt.
Operate the shifter to pull it into the middle-ring position.
The plastic wedge is released, can now be removed.
Shifting back down to the granny will now fall back *beyond* the position it was wedged in, as the powerfull spring takes up tension in the cable.
It should now sit correctly on the granny ring.
That's really all it should take.
