Well, I've come up with a kind of fix for this, which seems to work..
I created two simple 32x32 PNG images which had the curved borders on them, and made two launchers, and simply placed one furthest right, and one furthest left.
If the panel size is set to 12, the left one works perfectly, but the right one is nudged over 1px with a little line of the right side of the panel, which kinda spoils it.
A simple fix that I found, is to set the panel size to 25. This seems to knock both images aligned flush to the edge of the panel
without too much/no resizing of the panel at at all!
If you're interested in these images....
I'm open to other suggestions as to a another workaround for this; maybe we should start a petition
Try those if you want to be able to move other launchers/utils right next to the curve. Be sure to lock them in place too!
Also, if you can get the images correctly aligned using a larger scaled panel, you can lock them, and then scale the panel back down, and they should stay there!