I've been shooting 12 strand (loops padded to 14) for ~60# 30".
If the bow was made to AMO specs, the string needs to be 3" shorter than the AMO length, regardless of if it's a recurve or longbow!
Most bows, even those marked "AMO" aren't made to AMO standards though. It's best to measure the string on the bow when it's at the proper brace, then make the new string to that length.