You also need to remember that a flex-wing will alter in shape dependent on wing loading. As has been explained, the billow shift during roll makes turns a lot easier, but in pitch the luff lines will ensure the reflex creates a stronger pitch up 'feel'. Early hang-gliders had a tendency to 'tuck' in a dive before the reflex function was fully understood. The combination of reflex and wingtip washout ensures that pitch stability is maintained through the speed range. Obviously the more stability you have built in with reflex etc can also cause extra drag which is why modern microlights have adjustable reflex/luff lines. (I think, my hang-gliding days are, I fear behind me now
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