You're at the center of the sphere, though, so something is keeping you from falling [splat!] against the wall of the sphere you're facing. You look over your shoulder, and check it out...there's another invisible cone behind you, pointing in the exact opposite direction from the one in front of you. The pull of the second cone exactly counteracts the pull of the second one.
Okay. Now imagine that using sheer force of personality, you propel yourself forward through space toward the wall in front of you. The angle of the apex of the cone doesn't change. What hapens to the circle described by the far end of the cone on the wall ahead of you? It gets smaller. Feeling uneasy, you look over your shoulder at the back wall of the sphere...sure enough, the circle behind you has got bigger.
As you approach one wall, the circle behind you gets bigger and bigger, and the one in front of you gets smaller and smaller. The gravitational pull toward the far wall increases with the square of the distance from you to it...but the amount of far wall exerting that pull decreases with the square of the distance as you approach it.
The reverse thing is happening behind you...as you get farther away from the back wall, the gravity becomes weaker with the square of the distance, but the amount of wall exerting the pull is increasing at the same rate.
All other gravity inside the sphere...up and down, left and right...is balanced. You can construct these conceptual cones for any position inside the sphere. So, voila! Zero G regardless of position.
That's somewhat what I said at #23.
I guess I was putting too much "weight" on the gravitational factor and not paying enough attention the the inverse square law.
I was thinking that if you were standing on the interior surface, the small amount of force from the material under your feet would be overwhelmed by a larger force from the massive amount of material over your head.
Thanks for your insights. This has been interesting.