As I move around specific areas of the UQ are pulled tight or loose depending on my position. It seems the full length shock cord provides some dynamic "darting" to play-out or snug-up the different areas. Having shock cord only on the end does not account for this along the length of the UQ.
Static cord on the ends and shock cord through the channels may work, however, there may be more adjustment to both sides to keep the static portion on the end.
Given the small length of shock cord that could be swapped out, not sure it would be worth the hassle.