The RX-1 engine is not at all sensative to profile changes, if it is, your clutches could be way out of balance, basically the wide toque band makes it non-sensative. Remember, just because your engine rpm might seem sensative, at the clutch is 20% less change.
The problem with the stock weights is at altitudes over 7000' feet you cannot lighten them up enough. I found by grinding 1mm off each side of the clutch weight, I was able to keep that profile (which is best matched for the 4 stroke engine) but lighter all the way through the clutch stroke. I then was able to add weight to get my desired rpm's. I ran from 9500 to 10,500 and found it climbed best between 9800 and 10,000.
Running 89A and 8BU's or 8DN's, the profile is not matched for the 4 stroke engine, the rpm's and performance will be far too sensative.