One other trick to getting them to dig deep enough is to shorten the top link as it is dropped. As yours shows, when the 3pt arms drop the subsoiler tooth is pretty parallel to the cutting path (horizontal) when at a depth of about 8-10 inches. That means the tooth itself will not be pulling itself deeper, thus the need for weights.
I connect a chain between the subsoiler and the drawbar to pull on the lower shank at a point below the 3pt arm pins. This allows me to disconnect the top link, and makes for a more stable pull.
Just a different way to skin the 'cat' so to speak. /forums/images/graemlins/wink.gif