I don't trust the browser not to leak some info by things like doing DNS lookups so I wouldn't trust the browser for anything I actually need to have secure anyway; Torchat seems a better approach than a browser and if making the borwser actually be secure means installing a whole new/separate browser I might as well install Torchat instead, it seems simpler enough to give me more confidence that it is not full of as yet undiscovered holes caused by some stpud resource-hogging eyecandy or earcandy or mindcandy bell or whistle that adds more vulnerability for the sake of encouraging adoption by idiots...
-MarkM-
Foxyproxy is for switching proxy not making Tor browsing safe. Tor homepage is clear about this.