Out of curiosity, what size do you set your TC volume to, and what size is your wallet.dat? Is the possibility of wallet.dat exceeding the size of backup.tc a problem?
I can't imagine anyone's wallet.dat being that large... Plus you can always create new TC volumes. My wallet is under 200K right now. Alternatively, especially for such a small file, plenty of other per-file encryption schemes would be just as applicable.
