I've heard talk of the "tiller" issue before, but to be honest with you, I can't find any mention of having a special tiller for this type of hold in Ferguson's book, or any other book on archery that I own. If anybody can point out where this is a scientific problem,
I don't know if it is all that great of an issue. However, I do personally know that bowers will ask the style of shooting that you do and take that into consideration into final tiller adjustements.