The rhoades lifters were tested with high volume oil pumps, high pressure pumps, and different viscosity oil by Hot Rod back in the late 70's and they found that they don't affect the rhoades lifter.
As far as bleeding down at higher rpm.
How many times per second does a lifter cycle at an 900 rpm idle? :read2:
How many times per second does a lifter cycle at 6000 rpm? :read2:
Do the math, post it up and let me know. I'm waiting.... :-\"