Unison notes cancel out panning effect? (Strings instrument in FluidR3 Mono)

Hi,

Maybe this is a natural consequence, but I would like to get some comments over this. Using the latest (I tried with older versions too) FluidR3 Mono in my MuseScore 2.0.2, notes playing at the same pitches of (in my example) of the "Strings" instrument, which I use for Violins and Violas different staves, seem to cancel the panning effect I established previously in the Mixer - playing the unison without any panning. As said, this would be a normal consequence due to using this instrument.

Attaching a sample, it's in beat 3 of measure 3 and in the whole measure 4, where these unisons between violins and violas seem to cancel the panning.

I'm aware that we're talking about the same instrument, so that this result would be perfectly logical, but I wonder if it somehow this can be tweaked in any sort.