Changing volume with FSM432 and Expression pedal

Has anyone used the FSM's Control 1/2 to hook up an expression pedal to control volume?  I have a cheap wah wah pedal which I've gutted and set up internally with only a new 25k Lin potentiometer as per the FSM432 manual.  I have connected it to Control 1 and reprogrammed the FSM to set Control 1 to Channel 7, the Hard Volume.  I've also tried Channel 57,the soft volume, with the same results.  When I use the pedal in Preset Mode I do get some drop in volume but rocking back over the very last portion of the pedal travel it comes up onto full volume again.

It's almost as though the pedal pot has a shorting section inside near its bottom end.  I know the pot is a standard type, I've measured it and it checks out as a standard 25k Lin type.  I am also surprised to find the limited range of volume control this offers.  I was hoping to be able to bring it up from silence to full but the GM Volume control is a little compressed like this too so maybe it's not surprising.

Has anyone else had a problem like this or can offer an explanation?

Check the polarity? My memory might be foggy on this, but when I first got my GM I was experimenting with different expression pedals and I happened to have a couple Moog EP-2's lying around from my previous rig. I tried them with the GM/FSM and I seem to remember getting the same behavior that you are describing. I contacted H&K and they suggested it might be the polarity. The EP-2's polarity is not selectable, but the newer EP-3 has selectable polarity. I picked one up and tried it, and vee-o-lah, the taper became normal.