Hey Ozy,
I may get a bunch of flack over this comment, but i've found that a slightly weak shaft with decent sized feathers is the most forgiving set up for me.
I played with those itty bitty fletching and all the bare shaft tuning stuff till i was blue in the face, and came up with exactly what you just explained. As long as my form was perfect, the arrows flew great..... I took the same arrows and put 4" fletching on them and it made a world of difference....
The big one i've found with using arrows that are borderline on the stiff side is that if i get into a weird position where i can't quite hit anchor,i consistently hit left. And if I'm swing shooting, or wing shooting, a less than perfect release effects the flight much more than if those arrows are a tad bit weak...
Kirk