Your Su-Do-Koi should hover just fine You might be overloading the FX with a 12/3. Most people I know are using an APC 11.5-4 people are also using the APC 12.25-3.75 prop, but I feel that it does not rev up as fast as needed to get you out of a bad situation.

Next you will have to move the CG as far back as you can comfortably stand it that will help with hover and harrier stability.

Also Max out the control throw to at least 45 Deg. Use exponential to soften the center to your preference.

Here is the hard part the closer you are the easier it is to see subtle changes and correct them. It is far easier to make many small corrections than to make giant inputs. If I try to hover high in the air or 50 feet away it is more difficult for me but right in your face is easier.

These are my opinions.

BTW the morris sledge and the ohio models edge 540 are EXCELLENT flyers if built light.