Slider VelocityMode without acceleration?

is there a way to turn off the acceleration in velocitymode? I just want to have a fixed tranlation of f.e. 4 pixels of mouse movement results in one pixel of slider movement.
this question was already discussed in this thread but doesn’t provide a solution:

I have messed around with setVelocityModeParameters but couldn’t find a setting, that matches what I want. What I have found is the following:

        //if (mouseDiff < 0)
        //    speed = -speed;

        //if (isVertical() || style == RotaryVerticalDrag
        //     || (style == IncDecButtons && ! incDecDragDirectionIsHorizontal()))
        //    speed = -speed;

        speed = -mouseDiff / 1000.f;

If I apply this patch to handleVelocityDrag, i’m getting basically what I want (for linear sliders). The problem is, handleVelocityDrag lives in Slider::Pimpl. Is there a way to archieve this without changing the framework? Am I making things too complicated by overseeing something?