So that mean if you replace motor with 970 RPM per Volt with 760 RPM per Volt, you will need 970/760 more Volts for the same RPM. That makes 970/760=1.28 more volts. That means instead of 4 cells you will need 1.28*4 = 5.12 cells. So try 5 cell battery and hopefully it will be enough.
Question is, why you want large motor on such small model. I use such motor on 60+ oz models.
Probably inexperience. I was led to believe that a 12 x 6 prop at about 8,500 rpm was what I needed. The prop chart for the 2826/12 produces that (and thrust = nearly 2x the weight of the plane) from a 4s. 14.8 x 790 = 11,692 potential rpm. 8,500 should have been a walk in the park. Obviously I have something to learn, like maybe the prop charts don't work for CL? I have run the RPM up to 10,500 (Huben timer) with no change in power so all I can surmise from that is something in the ESC is preventing it or I have a bad motor. The plane was a tiger with an OS35s on a 10 x 6W.
Correct me if I am wrong here but one of the main functions of the ESC is to provide the required RPM's regardless of load and as long as the prop is turning at those RPM's it should deliver the power necessary to maintain those RPM's.
As to why the larger motor - I purchased it for a larger plane before deciding to convert the Nobler. The Nobler is overweight and a bit nose heavy from the 4s and has no room for a 5s. So, if nothing in the ESC can be changed and I cannot fit a 5s then I need a smaller motor to get more power. Some IC diehards told me I was crazy to go electric. I am starting to see why!
Ken