Radarr / unrar / post processing

So i really want to ditch Couchpotato at this point.....

but i'm stuck on the unraring / post prosessing, after reading i know that radarr doesn't do unrar , ok that's fine, i have rtorrent and such that can do that for me , but i'm reading radarr will try and import the file quite quickly and so you may get a corrupt file as its not finished unpacking.

Is there somewhere i can run a post processing script so that once rtorrent has finished it gets imported ? or is it just simpler to use drone factory ?