Mesa Boogie V-Twin pedal Clean Gain mod

[Bails]

I've already searched the forum, and was wondering if anyone knows the mod to have variable volume in the clean or blues channel of an earlier model Mesa Boogie V-Twin pedal. The volume levels, when switching from bypass -> clean/blues -> solo has no control. I think Mesa fixed this themselves with a trimpot in later models, but the available schematic appears to be the orginal version.