It might be possible to make a mold or have one made. I use 12 lb round cannon balls and find the blowback with fish hawk probe not that much different then the other side without the probe. You can find molds for them.
If you look close at that weight it looks like theres a hole in the fin to attach your release to I think that weight hangs down with the fin to keep it from spinning. I have seen other weights like that and thats the way they worked.