Bullseye does share lots of information about our products--I dare say, more than most manufacturers!
There are working notes for each glass style in "About Our Glass". http://www.bullseyeglass.com/products/a ... glass.html
Relative viscosity is often mentioned, so that is one place to look for info.
In general, transparent glasses are softer than opalescent glasses, and dark glasses are softer than light glasses. 0100 Black and 1412 Light Aventurine Green are the softest glasses, and 0137 French Vanilla may be the stiffest glass.
I hope this helps. If we ever release the info you requested, I will post a link here.