From experience, sustained 10-12 knot wave lift for 100km or longer
sections of the Sierra wave is common enough so that a 200knot redline
can make a significant difference. Doing the math, so long as I have
about 10:1 glide @ Vne that's good enough for me. Selecting a target
indicated cruise speed of say, 120 knots at 17.5K ft. (true 160 knots)
I can push over to 145 knots to handle the lift spikes of 12-16 knots
before having to go upwind to reduce the climb rate. This then allows
me to track straight and modulate altitude with airspeed-only making
for a better net ground speed. Without a Class A clearance, IMHO this
is the only way that a 3000km flight is going to be done in the
Sierra.

Kemp