Digital BW, The Print

From what I've been reading, a lot of people in this forum using the 
QTR software use the Lab-to-grayscale method in PS to convert their 
images to monochrome. Is this method suggested when using the QTR?
I only ask because I never use that method, instead I use Petteri 
Sulonen's (black & white negative with tonal controls)

http://194.100.88.243/petteri/pont/How_to/n_Digital_BW/a_Digital_Black_
and_White.html

So by the time I get my image into the QTRgui, it's pretty much where 
I want to be. 

Does my method of monochrome conversion create limitations?