Do they have to be 7ths? To me using major chords has always sounded right also; a little less "clichéd" blues.
... and that's all I have to say about that.
[U]ALL[/U] generalizations are [U]WRONG[/U]
[/sarcasm]
[U]ALL[/U] generalizations are [U]WRONG[/U]
[/sarcasm]