Flip around the center of the drawing

[schwarzgrau]

If I draw a walkcycle in front view I usually sketch the first step of it, duplicate the layer and flip it horizontally to keep a similar speed for the second step. Unfortunately TVPaint always flips around the center of the working space, but at least for me it would be a lot more handy to flip around the center of the drawing (like it's done in Photoshop, if I remember correctly)
Maybe it's just a personal preference, but I would love to flip around the center of the drawing.