KActor Touch problem

[Jereak]

Hello everyone !
I almost find every answer I need here (very nice forum !), but now there is an exception. Even with hours and hours of research, I can't find the solution to my problems, and that's really frustrating !

I work on a game where the player can control a ball. This ball is a KActor and normal collisions (with the world) work well, the ball can roll and move as expected. However I have some problems, particularly about "Touch" detection for the ball.

For example, if I have a TriggerVolume, the "Touch" event with the ball is detected using the bounding box of the ball, and not the ball itself. That lead to very strange behaviors sometimes, especially because this bounding box is moving and scaling all the time... strange, like if the ball was in fact a rolling cube, and not a sphere. Here is an image illustrating the problem, you can see the "Touch" log to the left when the blue box has just entered the TriggerVolume :

Touch ! That's wrong !

--> How can I say to volumes to "Touch" with the yellow bounds (the sphere bounds) or the simple sphere collision instead of the strange blue bouding box ?

A second problem, that may somehow be related to the first one, happens with collision components with my actors (actors that I create in UnrealScript for example).
On the following images, I have an Actor (let's call it A) on the center of the circle that have a cylinder component for collision component. The ball doesn't "Touch" this collision component like TriggerVolume before. On the next image, we can think we see a normal behavior, because the blue bounding box of the ball touches the cylinder component and the bounding box of the actor A, and there is no Touch detection (top view) :

No Touch ! This is normal.

The problem is that the "Touch" event happens when the ball enters in the bounding box of the actor A, instead of the collision component (cylinder) that I defined for this actor. Like here (top view) :

Touch ! That's unexpected !

I would like the ball to "Touch" the actor only when the ball touches the cylinder component, not its bouding box. In fact, I don't know if this red volume is actually the "bouding box" of the actor A, because it only shows up with the "show collision" command and... it's red. But I never asked for this red collision volume.
--> How can I solve this second problem (with properties, unrealscript, ...) ? Maybe the source of this problem is the same as the first one above.

In the ball Mesh properties, I have unchecked "Use Simple Box Collision" and "Use Simple Line Collision" (it is even worse if I check these). I also tried to change the collision type of the TriggerVolume and the actor A, but it leads to nothing. Where could I look now ?

Thanks for your time reading and helping me.
Have a nice day.