Daughter is now 15 and plays a ton.
I string with MSV hex and prince SG. Also use HEad sonic pro when out of MSV. She can't tell the difference. She's got a big swing and has gone through a full bed of SG in about 4 hours.
MSV mains at 56 and the SG crosses at 59. She loves it and I usually cut it out after about 15 hours.
I too have heard the full bed of RPM blast at 54 but haven't tried it yet.