I use generic strings like Martin Marquis, I believe. I get the phosphor bronze light guage, standards, like you use. The Santa Cruz I used to have that I used for that tuning really took the low C well and the strings didn't whimp out. I think Martin Carthy uses slightly heavier gauges (at least he mentioned something about that on a video I got a few years back). I tried elixer light gauge strings as well, but miss the bronze wound fret buzz (not really a buzz, but there seems to be a bite with those that the elixers lack, so buzz may be a poor term). I generally get the strings a dozen sets at a time, for a decent price. I suspect I can get away with the lower tunings on light strings because I'm not playing real hard most of the time. Hope the info helps.