Pretty sure this is not possible, '@' is a symbol as is regarded as such, in the 'clan tag rules' there is written that you need symbols around your tag and the tag is a letter or a number.
Also, you can use it without having the clan or added name, [ @ ]prozajik, works without any problems even on sv_login 2 server, thats another clue that it probably wont work.
Lastly, if the tag would be possible, it would be 100% taken, as all one letter and most of two letter tags are taken already.
But jitspoe might make it happen even tho i doubt its possible.
PS:The [EDIT] button is there for a reason, i would have guessed that you already knew how to use it with 200+ posts, its kind of useful especially in situation exactly like yours.
