Yes. Off the wind
easing the backstay - even with a very stiff mast
like mine - makes the headsail shape nice and soft. It also helps generate lift
at the expense of pointing in light air. Cranking it down makes an incredible difference in pointing when the wind
is strong enough (10 kts or so on my boat).
Look at mechanical backstay adjusters and compare the prices with a rebuild
of your hydraulic system.
If you have running backs your probably have an inner forestay. The running backs keep the mast
from pumping in heavy air from the staysail loads.