Thanks Pattye, that's help me make sense of all this knotting strategy! I have to say I really love both Beader's Secret and Powerpro. The Beader's Secret is softer and on my hands, the variety of colors is gorgeous, and the drape is really ideal! But I think PowerPro is more forgiving for newbie knotters like me. Also, I think it is better when strength is the primary concern, such as knotting with beads, I would prefer Powerpro. But I will also try Pattye's idea of adding another thread for larger holes.
Actually, I don't see any reason to use silk at all anymore--it gets dirty and it stretches. However, I just watched an instructional DVD that I purchased because I really want to learn the proper, professional way to knot. The instructor said to use silk for pearls valued over $500, otherwise she used another synthetic. Does that make sense to anyone?