I have two Edge 540s. The VF CGs upside down better than the 120 size other brand. You should be fine at 4". If it acts like everything is twitchy on low rates move the cg up 1/2" and try it there.
What kind of radio do you run John ? If it's got 2 to 3 rates available we could all pitch in and post our rates and expo settings .
I use Futaba so it's going to be alot differant than say a JR or HiTech.
Running the mighty OS.91FX here as well. Found the perfect prop for the VectorFlight. It's a 14x5 narrow bladed APC. Let's the rpms rev up but keeps the plane slow enough to dance. I got my low end set for a good clean idle and dial in the high speed backing off about 4 to 5 clicks richer. I found that the motor is more reliable like that and as you gain altitude the engine naturally leans out.
If you can get use to mixing sort of rich on the ground you'll have less deadsticks. Don't ask how I found this info out the hard way.[]