I posted some suggestions in the Recuva forum related to secure deletion, here:
http://forum.piriform.com/index.php?showtopic=26744
Many/all are equally applicable to the CCLeaner "secure delete" option. (Note that some of these things are already done in CCleaner, and so might differ from what needs to be done in Recuva, which is where I posted this originally. Also, some of these things might already be done, but I might have thought otherwise because of errors in my testing.
If I had to highlight one point for implementation, it would be to (if possible) move files to a randomly named directory off the root before they are securely deleted. That way their paths are not saved in the MFT even after the files themselves are securely deleted. A lot of information can be gained from seeing a path.