Seeking suggestion on creating a blend between 02 curved surfaces

Hi all,

I'm modeling a toilet seat and try to create a blend between the toilet bowl and the frame (please see attached photo and CAD file, v2013). I tried boundary surface and knit surface, but haven't succeeded to make a smooth blend surface between them as well as knitting all the gaps to make it a unibody toilet seat.

Any input will be highly appreciated.

Thanks

Kevin

SolidworksSurfacing