In a bid to answer my own question about how to tell the ply of a yarn that is not labelled, I did some more research and found this link which would seem to answer my question. http://www.knitting-naturally.com/yarn-comparison-chart.html. I'm just about to print out the information and put in my crochet folder. I'll be very interested to see what the thin 8 ply yarn comes in at.
Thank you for putting up with my grumbles.