Doc, see what the Jagg folks have to say about flow with their adaptor versus the H-D version. The adaptor/thermostat would be the thing to dictate how much oil is routed through the cooler, and if as you say the '07 and later system isn't routing enough oil through the cooler then perhaps Jagg's adaptor would help. Since you've already gone this far, one more change with the adaptor might be worth a try. And I would still question how much oil is really going through the cooler versus how much is going through the less efficient crash bar "cooler". You might want to temporarily restrict the flow to the crash bar and see if you can detect any temp difference.
BTW, have you verified that the stock thermostat is actually opening fully at the correct temp? If H-D didn't change anything recently, the specs for the thermostat are:
Start to Open - 180°F
Fully Open - 210°F
Jerry