One of my projects is a compromise. I am making my arms 5 1/4" long. I am using 2306 2050kv motors. When using 5" or 6" props it should boogy pretty well. Not like a 250 racer ( I'll be closer to 310) but exciting enough for now. When I want to slow things down and get longer flight times I'll have just enough room for 8x2.7 props. With the 8 inch props I can use a larger battery and am looking for at least 20 minute flights. The longer arms will slow things down enough to suit me when using the smaller high pitch props. None of this requires me to change any settings, just the props and battery. For yours, just look on line for motor mounts and pick the ones that suit your arms and motors. They will give you at least an inch in arm length. The drawback is your wheelbase will no longer be square unless you can angle each one slightly forward in the front and slightly backward in the rear. That should get you close enough to not upset the controller. With some care angling the mounts you should be able to do what you want cheap and easy.