Randy,
 If its the motor I think it is, I can provide a link if you want, then you can run any setup that we normally run with the Power 25's from E-flite. (4 cell lipo and a 12x6 apc or 13x4.5 or13x5.5 prop or similar)
William

HI Will

It is the HP I sell ( 3 bearing motor very similar to the AXI 2826 series), I know about the setting up for the same as an EF motor, I was curious what the most efficient setup would be, and If the 5 cell would be recommended.

Randy if you used an axi 2826-12  at 760 KV the 10oz batt can be used. Even better is the 720 KV motor Tim suggested.William D also recommended the Cobra 2826-12 5.8oz 760 KV. If you have a larger model the cobra 3520 at 700 KV 7.5oz can also be used with that batt.  Eflite  32 is Aldo a choice a little heavier.
All motor have been used with TP 2700 5S Batt.
Jose Modesto

Alas, the 720 kV motor I suggested is a product of my fertile imagination, so there may not be one out there.

Randy, in theory running such a setup would be perfectly fine -- but that's if you ignore switching losses in the ESC and iron losses in the motor.  I know that driving motors in similar circumstances in industrial equipment can be done with reasonable efficiency -- but it depends a lot on the amplifier (ESC) and the motor -- and I simply do not know how a Castle ESC and your motor would behave.

If I had the necessary stuff on hand, I'd just try it.  Any smart old engineer would do the same thing: there's just too many variables to work through this by theory.  Put the motor on a stand with a suitable prop (probably a bit less than a flight prop, because you'll be running it on the ground).  Run the motor at a given RPM with each battery while monitoring the battery voltage and the current into the ESC.  Check the power used by the motor/ESC in each case, and check to see how much the battery voltage sags.  All your answers will be there.  All you need is a voltmeter, a current meter that can do 40 amps, and a test stand.  Or, a Wattmeter and a test stand.

Randy been there done that with the KV motor you have, even my 5S 4000 dint work drained Batt 3/4 way through pattern.
Just my opinion
Jose Modesto

Hi Randy,
With a KV of 900, this is a 4 cell motor. You've got that already.
How big of a capacity? Depends ... figure 0.6 watt-hours per ounce of all-up weight just to fly the schedule. Add another third to half for proper margin and to avoid over-discharging.
When you cut capacity thin (like using 80% to make a flight) the lower C rating batteries (17C to maybe 25C) may not cut it. This is when low voltage cutoffs kick in as batteries age or on cold days.
Upping the C ratings often costs as much weight as running bigger capacity 25C batteries and having 30% or more of the capacity left after the flight.

Often there are two good combos: one with less margin and high C batts, and another with lightweight packs and more capacity margin. My guess is that the winning (lightest) combo varies with airplane weight.

Then throw in the 5S vs 4S thing and the number of sweet-spot combinations multiplies, provided you have motors with the right KV's.

I haven't answered your question, have I?
Dean

Hi Randy,
You mean Nobler-sized?

Dean