Solidworks Trim/extend issue

[yellowtruck]

I am trying to properly trim a weldment intersection however it is not doing what I want it to.
As you can see below "Allow extension" creates the extra bit of material at the end of the weldment, which is not desired !

However without "allow extension" the "concave" corner is square, and I need it rounded like in the other pic.
Any clues ?

http://files.engineering.com/download.aspxfolder=21249602-78 9a-4a5d-b72a-0fa9aceb269d&file=no_ext.png


http://files.engineering.com/download.aspxfolder=0e4eec3f-84 8c-4990-95fb-991b51f6061d&file=ext.png
Edited by: yellowtruck