My J/122 has a below deck furler. It totally sucks. More friction and less leverage means I either need to turn downwind or put the furling line on a winch. I’ve comfortably furled bigger headsails by hand with above deck furlers.
Safe stanchion height is relative people size not boat size. So it’s not gonna change to stay in proportion with a smaller boat. But I believe some J/100s were sold without stanchions and life lines if you need the purity of driving without your seatbelt.