A retired tractor mechanic who put in 40 years fixing JD's, Case, IH, Kubota's and several other brands advised me that generally 2000 RPM or so for most all FEL work is fine unless more power is required. Then he said, give it all she has! He feels that running at full throttle at all times only wastes fuel and you really do not gain any benefit unless you are pushing the machine to it's limits. I tend to believe him since he has repaired most everyone's tractor that I know and they all call him the wizard or "doc".