Hi Andy,
I don't have this suggestion in my system but I know someone who has build it and is very happy :-)
I don't know if he uses both objects parallel.
Here is the link to the SAP help:
for me it sounds like both objects can work parallel and there is only 1 switch so you can test it in an development system and switch it off if you don't like it :-)
the P_NNNNNCON is an custom object with the fields TCD for your PA30 or something like that and INFSU for the Infotype and Subtype.
It's only an idea but for what I heard and read it sounds like it could work in your scenario.
Good luck
Lars