Boss SP-1 Spectrum (parametric EQ) - mod for Q?

[aion]

Original schematic for reference: http://i1249.photobucket.com/albums/hh506/aionelec/sp1_schem-1.png~original

I built one of these and it works as advertised - not terribly different from a fixed wah, but maybe a little more subtle than I'd hoped, even with the Balance control turned all the way up.

Since it's a fairly simple circuit overall, I'm wondering if there are any easily-identifiable spots where components could be swapped out, either fixed or on a switch, to alter the Q (width) of the parametric boost?

And while we're at it, are there any other easy targets for mods that might be interesting? I noticed that there was a really narrow sweet spot for guitar, and that the high end of the spectrum was way, way too high to be useful. What about bringing down the frequency of the high end so that the overall range is smaller, to make it more useful for guitar? Does C8 set the upper end of the range, such that increasing that value would reduce the upper end of the range and make it easier to dial in the mids?