Hi Branden, so once you do the fillet on the non-solid object in the 3DM file from the post above, the cleanup goes something like this:

Select and delete the weird lumpy corner:




Now this fillet needs to be trimmed better:



To untrim and retrim it start by selecting it and run Edit > Separate on it to break it out into its own individual surface not joined to the others anymore. Then select that lumpy edge at the end and do Ctrl+A to select all of its edges and then hit Delete to remove the current trimming boundary and recover the full underlying fillet surface. Note that the full fillet sticks out a ways past the other end as well.

So after the untrim you've got something that looks like this:




Switch to the Back view and draw in a curve like this (use tangent snap on the second point, and drag out a tangent construction line on the second-to-last point so the curve is tangent on either side):





Then trim the fillet with that curve, so you have this:





Then join those surrounding pieces together (also the other end of the fillet needs to be trimmed back also), then you can put a Network into this better shaped hole.

- Michael