The Reform Group website has a number of articles on it pertaining to Unionism in the Irish south. I've linked to a couple below, but do check out their site. You can also contact Reform - if anyone does, let me know if they respond, I've not got hold of them yet.
Edit: Also found this interesting take on Sinn Féin's development. From the look of the guy's blog it doesn't look like I'd agree with him on too much else, but his analysis is nonetheless interesting and he's a fellow integrationist, so no harm in linking.