relay in background?

A while back, I setup a couple of radacct relays for archiving using the new mechanism, however occasionally the archive server is slow (the reason we moved the archival process to another server to start with), and it's impacting the primary because it doesn't respond until the proxying is done. With radrelay, this is done independently and it doesn't matter if it gets a little behind. Is there a way to make the builtin mechanism behave in the same way? If not, I'm going to resurrect radrelay...