Can't vote as I've only tried it with a TMWH.
However I did struggle in the beginning but when I added a curve of 22 it worked out beautifully and connected first go. By third attempt I was already holding it for the full duration of the refuel.
Just a week ago I decided to set the curves back to 0 on both axis. Managed to connect fine but probably had about 10 disconnects before I got a full tank. With more practice it shouldn't be a problem...
The 40 odd hours you've put in won't make a difference if you're just replicating the exact same thing you've been doing for the last 39. That'll only end up with the same result. Instead try to do something different each time and see what works well. I know it may seem obvious but we all may not realise it and unless your controller is faulty (check the curves in windows?), 40 hrs of proper practice should be way more than enough.
What stick are you flying with now?
Btw man what a difference 0 curves make. The A10 is now suddenly a nimble beast whereas before it was quite sluggish. I'd recommend 0 curves to all if possible!