+1 for non uniform scale. I find that to be a huge flaw in this unwrapper. I'm jumping from RizmoUV to Maya way too often because of this little, so obvious thing I can't do : X or Y scaling instead of uniform scaling. Rizmo most definitely needs that.
I would like to suggest a way to quickly adjust the radius for this without having to reach over to the right panel every time. CTRL+RMB Drag feels (to me) like a familiar way of doing this from other programs. This would also be useful for drag, spread, and pinch edit modes.