Synthetic cable over Nylatron Sheave

I'm looking for someone experienced with running cable (synthetic or
steel) over Nylatron (or similar synthetic) sheaves (pulleys).  We are
looking at running a synthetic cable over "dead" (static)sheaves at up
to 350+ fps.  There will be approximately 15,000 lbs tension in the
cable.  To make things worse I also want 5 - 10 years of life.  We are
searching for the dynamic holy grail, the massless, frictionless
pulley.  Anyone seen it?