I think the most I ever tuned mine down was one whole step and it was rough. Had to let the screws in the back out quite a bit. For something that low, I would think you'd need at least .11 gauge strings. Definitely something heavier than standard. Playing .11 gauge strings in standard tuning would be worth a tip of the hat. The screws that hold the spring assembly in are fairly long, but not certain how far you can unscrew them, so that they remain stable, i.e. don't know how far you could safely detune it. People obviously do it, though. Just not my area of expertise, unfortunately.