Larry, 
It should be OK. I use mine on a Kubota 
L4310 which has ~7-8 GPM of implement flow. Here are some details (mfg phone#, specs, and a toll free number). 
    McMillen Construction Equipment Attachements
    Phone 800-234-0964 or 219-747-6750
    4419 Ardmore Ave.
    Fort Wayne, Indiana 46809
Specs: McMillen model X450 
    Minimum Hydraulic Flow 5GPM, Maximum 10GPM
    Max Hydraulic Pressure is 3000lbs
   GPM   =  RPM
   5   =     65
   6   =    78
   7   =     91
   8   =     104
   9   =     117
   10  =     130 
The dealer told me you need at least 85-90RPM under no load to spin/shake the dirt off the auger once it is out of the hole. I rarely use full speed while digging (it digs to fast). 
Torque is specified as follows:
   PSI   =   Torque (ft/lbs)
   2000 =     470
   2100 =     493
   2200 =     516
   2300 =     540
   2400 =     563
   2500 =     587
   2600 =     610
   2700 =     634
   2800 =     657
   2900 =     681
   3000 =     704
I do not have a clue how these specs compare with a PTO driven auger. One nice thing I see is the specs are basically independant of your tractors PTO horsepower and size as long as the flow and psi are within the ranges stated. Not sure if it really matters though since high horsepower will just break shear bolts. 
My owners manual shows that McMillen offers a complete set of mounting options (Skid Steer, Backhoe, under or side Bucket, 3PH, 3PH with downforce). FYI// This is the smallest unit McMillen makes. It looks like most of their stuff is for full size backhoes and excavators. 
Hope this helps. It sure feels good to contribute something to this board. I have been lurking (I mean learning) for a ~1 year.