Please stop ruining this part:http://www.bricklink.com/catalogItem.asp?P=2339
I do not know what has possessed you to alter the underside of the arch so that it no longer clutches bricks, but I have found myself overlooking any and all sets that contain high numbers of its inclusion (2x) because it is inferior to a part that once looked like it, yet did the job better. Why the change? Doorway and window arches still clutch bricks inside the arch, so why not the half-arch?
Please destroy your current mold and cast it over again, because it appears as though you have goofed.
A Shrinking Forest
There is no life I know to compare with pure imagination. Living there, you'll be free if you truly wish to be. -Willy Wonka, 1971-