The clubhead , the Hands, the direction of Thrust all approach the ball from the "inside" just as the Plane dictates given any angle of inclination. Picture it from down the line......to move down plane is to move Out and Down towards the Plane Line.
A straight Plane Line has an associated Inside out approach given any inclination to the plane. A vertical plane would have only down and no out. A Horizontal Plane would have only Out and no Down.
Per 2-J-2 ".......Though its an "Inside Out" Impact its not an Inside Out Stroke unless the Plane Line crosses the Line Of Flight as depicted in photo 10-5-E" (Closed , Closed).
So in other words the direction of Thrust is not "cross line" or "across" like you say unless you construct a cross line , closed Plane Line and then thrust down and out along this new plane towards its Base Line. Thereby thrusting out "across" the original straight plane line.
To get the Down and Out along the plane, it seems that I have to have the "feeling" of across. When I have the feeling of "down the line" it results in a big pull. Of course, too much across (like you've described above) and big hook (that starts down the line and turns over like a top spin forehand in tennis!).
The side arm throw feeling actually captures what I feel when I hit good shots, but I was concerned that I was "switting" and didn't want to ingrain that feeling. Also, cannot believe how slowly I can swing and hit really crisp shots. Tempo has been a real challenge, but one worth fighting.
I got into the whole "hitting" vs. "swinging" because I've been away from golf for 6 years and want to develop a more consistent approach to ball striking. I've always been streaky -- tour caliber shot followed by cold top, a fat one, then another 9-iron to three feet. Way too frustrating. Hitting seems to offer the control (plus I'm getting near 50, so flexibility is fading!).
Been lurking here for a year, but am thankful you guys are willing to share.