Uncle joe,...
I can just go along with what some other people have to say here. With 1600hrs fixed wing and having just passed the R22 ride, you are taking, without any offense, a pretty good chance of becoming a statistic by practicing solo autos.
I know it is very tempting, but for your best, leave it alone. Practice with an instructor and hope for the best if you should have a real engine failure on your own.
As for the RPM- the R22/ R44 is not a very forgiving machine. As long as you are above the minimum aircraft weight, which a normal R22 with standard equipment and at least one pilot oboard
always is, you should be able to contain and maintain RPM. If not, you may have an engineer check the rigging of the blades since it seems very strange.
Now when you are light, yes, you may not be able to recover or only slowly recover the lost RPM.
Don't listen to suggestions of having your RPM down below 90%- there is no need for it and by the end of the flare, every percent counts.
The only time you could consider the RPM in the mid 90 range is if you are looking for the max glide distance.
S-turns as someone suggested, doesn't help. You may increase the loadfactor temporarlily, but as you roll out of a turn you are back to square one. However, it is a good way of adjusting your glide distance to hit a spot.
The pedal input will not have any significant result on your RPM. Yes, it does create more drag on the aicraft if you are out of trim, but that will only increase your rate of descent, not affect your RPM.
If you ever should have the chance, attend the Robinson Pilot Safety Course.
For the meantime, please, may I suggest agai to stay away from solo autos, it would be a pitty to read about you in a safety bulletin.