Thanks for the replies. Here is some stuff I picked up from the net.
"I've been wondering the same thing myself, I haven't tried it yet either.
Here are the specs though.
D10=.016 dia. @ 115 lbs. SS break strength, 100% SK78 Dyneema.
D97=.016 dia. @ 110 lbs. SS break strength, 100% SK75 Dyneema.
So, D10 is five pounds stronger, creeps a little less and costs $8.00 more than D97 for a 1/4 lb. spool.
Here is the response from BCY.
Dynaflight 97 is made from, what was, the best Dyneema yarn, SK75. Tough and durable. Low creep. Used on compound and recurve bows.
Dynaflight 10 is made from what is now the best Dyneema yarn, SK78. Very little difference in strength and durability but even less creep. Same size as D 97. Same colors available. Just a little better product because of the lower creep.
I got in some Dynaflight 10, and built a few strings with it. I had to make my string 1/2 inch longer than my normal dynaflight 97 strings. When cutting my flemish strings I can tell the dynaflight 10 is stronger (harder to cut). So far a lot less creep with the dynaflight 10. I have shot some arrows through the string and don't notice any difference in sound, but my arrows are acting slightly weak now. Not a huge difference, other than there is very little creep with the Dynaflight 10. I will see how the strings act over time."