As has been mentioned before, there is DEFINITELY a market for high end 7's. Would it be feasible for PRS to tap into this market? In 2015, I would say yes. The guys who grew up in the nineties are becoming professionals and have the expendable income for high end PRS guitars. They are also the ones who play and listen to music that utilizes extended range instruments. 15 years ago, 7 strings were more a niche thing still and the majority of guys who would shell out for a high end PRS weren't looking for a 7. Now is a cool time to be a PRS fan because you have such a range in the lineup! As for strings: Infeld Power bright 10-50's tuned to standard/drop D.