I guess I didn't fill them because I don't find them to be "ugly" and it makes things easier on the alignment guy "I'm an Industrial Mechanic as a living and tend to like things easy to work on". I've looked at them and thought about it but decided to leave them, I see no reason why you couldn't and agree you could just make a small hole for the break line "it's just going to make alignments a two man job". If you want them filled then fill them especially if you go with a different suspension "it would look better".
I'm still filling in holes now, so I've got time to think on it while I continue. I'm still thinking AlerKtion, or MagnumForce . . . not at that point yet. Understand and agreed on the making it easier for the alignment - but, it's not like you have to do that every weekend ? ?
Also, Did you also go through the entire compartment and weld up every seam and smooth them ? It looks like you did - love the way it turned out !
Sometimes Advil works for the headaches ( snicker ) . . .