FWIW I wait until the cargo schedule goes out before booking widebodies, and I've never had it change to a narrowbody.
I'm with
S80 here. All my October bookings with new widebody routes showed up on the October Cargo schedule when it came out(and confirmed all the little one off days too). If it's on Cargo, chance on swap is low or none! Very pleased with AA, J is usually less than double the cost of Y for most my flights too.