Well, looking at above numbers differences are minor, you can get much more from higher FSB with lower timings than from lower FSB with tighter timings on nForce. But It all depends what you expect from your system and what kind of benchmarking Sandra use.
If you want to set records this is the way to go, if you want fastest system I'm not sure if Sandra scores are adequate to real world usage here. In RL apps you more benefit from lower timings (except mass data bandwidth hungry ones like video/graphics editing). I think you should select some typical app which can be used for precise measuring (calculation program, game, 3dmark, 3D renderer) and fire up some runs with different mem settings.
As for strictly TRAS there seems to be just 2-3 options - lowest possible, 6/7 and 10/11.