The goal is to have the trailer level, and to have all lost weight returned to the trucks front axle. Without a doubt, using the 5th link sounds perfect, as the trailer is level, and the front axle well height is returned to it's original 36.5".
Some would say that if your front axle can handle a little extra weight, that the goal should be "equal compression of the front and rear axles". So you might even try the 4th link. Either way, 6th link does not sound like what you want.
PS - Weight distribution (10-15% on the ball) affects tendancy to sway more than trailer level. Being level is more about (IMO) wind resistance and keeping weight distributed between the 2 axles than actual stability.
thebrakeman ('70), DW ('71), DD ('99), DD ('01), DD ('05)
2004 Surveyor SV261T (UltraLite Bunkhouse Hybrid)
2006 Mercury Mountaineer V8 AWD Premier
Equal-i-zer WDH (10k), Prodigy Brake Controller