Yes Sir,
Trading Post is a good way to go.
My white tail leg sinew averages 9 to 11 inches in length.
The white tail back sinew can be up to 20+ inches long..
Following the volume of sinew used to back a 60 to 65 inch bow with two to three courses of sinew.
I have been seeing folks use 4.5 to 5.5 ounces of processed sinew per bow.
For me that has been working out to 4 to 5 Back sinew per ounce.
Or 3 to 4 Leg sinew per ounce.
You typically get more strands of sinew out of Leg sinew.
However you get more waste, and the strands are generally shorter.
Not to mention that Leg sinew is more work.
I have some leg sinew available for trade.
And some Back sinew...
-gus