I have a similar problem FYI - 5'11" and I ride a 54.5 effective top tube - however, over the last year I've moved from having quite a stack of spacers and a 100mm stem, to an negative rise stem and a 120mm - just through stretching, building up lower back muscle and gradually adjusting my position on the bike.
I have a similar problem FYI - 5'11" and I ride a 54.5 effective top tube - however, over the last year I've moved from having quite a stack of spacers and a 100mm stem, to an negative rise stem and a 120mm - just through stretching, building up lower back muscle and gradually adjusting my position on the bike.