There is no reason to complain about head tube length until you've got a 73 (-17) degree stem and that's not low enough. Then you can complain. An 84 (-6) is a full 2cm higher.

That said, If I was to buy a size S (51cm) LOOK 586, I'd be using no spacer and a 73 degree stem, with no easy way to lower the bars, except with a 67 (-23) degree track stem.