I'm not sure I'm understanding what you're saying. Usually when people tune their guitars down a whole step they'll play in the same positions they did before. Ex.- Somone who plays in G Maj/E min all the time will tune down a whole step and end up playing in F Maj/D min without even realizing it. And as far as playing on a seven string... if you like the sound that you're getting by tuning down a whole step you might not like the sound that you get out of the low A which would be the case if you tuned a seven string down a whole step. Also, there is only so far you can go, as far as tuning down goes, before you start to cross frequencies with your bassist. Which, as you know, will create the "muddy" effect that people run into when tuning down.