Access FilletSrf functionality from RhinoCommon

Hay guys,

I am looking for a method that would preform a fillet on two surfaces and trim them accordingly - just like the FilletSrf command. I can only find 

Rhino.Geometry.Surface.CreateRollingBallFillet(Rhino.Geometry.Surface, bool, Rhino.Geometry.Surface, bool, double, double)

&

Rhino.Geometry.Surface.CreateRollingBallFillet(Rhino.Geometry.Surface, Rhino.Geometry.Point2d, Rhino.Geometry.Surface, Rhino.Geometry.Point2d, double, double)

& 

Rhino.Geometry.Surface.CreateRollingBallFillet(Rhino.Geometry.Surface, Rhino.Geometry.Surface, double, double)

They all return an array of surfaces Surface[], which only includes the fillet at SurfaceArray.[0] without the two trimmed surfaces. Also it doesn't work well with non-rectilinear surfaces.

Any ideas appreciated!

Thanks!