I do the auto-split of my STK-S6 when in neck or bridge with an SSL-1 in the middle. I remember Frank Falbo recommending it for a better quack but never compared stacked vs split tone. I just do it to avoid buying a Super Five Way switch and the SSL-1/2 is easier/cheaper to find for me. By the way, the SSL-1 is the regular one, no need for RWRP in the middle when using any of the Duncan STK pickus, this was I still get hum cancelation.