Also one other note - to get a nice clean result it would probably be best to drop some of those vertical lines all the way down from the top profile, like this:



Then you can get a kind of cleaner result without any extraneous edges in it:



I've attached the .3dm model file of the result here.

Also one other note - since your piece is symmetrical once you have build one piece of the corner you can actually generate all the other pieces by Transform/Mirror which is faster. You can use the midpoints and corner points of the top profile to snap the mirror line on to, let me know if you need more info on doing that part. That would actually work for the Lofted pieces as well actually, you can just do 1 Loft and the use mirror to generate the other 3 loft pieces.

- Michael