Plethora X5 and the expression pedal used as a volume pedal is linear and I'd like to make it logarithmic

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Hi. Recent buyer of Plethora X5 running 1.2 firmware. I've just bought a Roland EV-5 expression pedal to use with the X5 and I've made it be the volume pedal on a board BEFORE the first effect in the signal chain. Trying to use it just for volume swells, it sounds like it's working in the linear fashion you'd expect from an expression pedal. The first 50% of travel is very quiet/useless and the last bit of travel is very sensitive/hard to control. I'd like to make it sound like it's linear, which means it needs to behave like an logarithmic analogue potentiometer would behave when it's being used a a volume pedal. Is that possible? FWIW, using an EX1 epression pedal on an HX FX as a volume pedal worked fine - but that was using up an effects block slot and presumably mapping the pedal movement to simulate logarithmic rather than linear. 


I realise I can do it in a Toneprint, but I'm hoping to do it as a global setting when it's not assigned to a particular effect, just controlling volume on the X5 in general. Doing it on a Toneprint-by-Toneprint basis is far too time consuming. 


Thanks for any feedback.