Probably a dead end academic question but has anyone experimented with sinew from the Ostrich or any other large flightless birds?
What brought the question to mind was a video on a device a guy recently created to mimic the ability of of the Ostrich's leg tendons to store energy of it's feet impacting the ground and release it for the next step as it runs.
Wearing his device he can run at 25+ miles per hour for extended periods.
These tendons look to be very long and might be useable as a backing material.
I'm sure we have some members from down under.
The Aborigine seem not to have taken to the bow, preferring the Atlatl other ranged weapons, so I doubt there is much historical data on the subject. They may have used it for bindings I suppose.