Ok, I just re-read the article the OP was referring to in Photo Techniques Jan/Feb 09'. The authors were just determining whether or not split grade printing could produce contrasts and curves that are unachievable with a single filter. And they determined that it could not. That's fine, but it doesn't mean that split grade printing is useless. So for what they set out to determine they did a fine job, but there are many advantages to split grade printing beyond the few factors that they found no advantage. So don't let the article sway you from trying split grade printing.