MaxX, MaxY, MaxZ (and related) update

[Miroku]

Hi everyone,
I know maxX, maxY and maxZ are very useful functions... but when you
alter an object property (e.g rotation) they obviously change... or
should.
In fact if I make

bgplane = new Plane();
bgplane.width = 300;
bgplane.height = 250;

I get a maxZ of 150.

But when I update the plane like this:

bgplane.rotationX = 90;

I should have a maxZ of 0 (since now the plane is perpendicular to z
axis)
but instead I get the same 150 value =\

I've tried using bgplane.updateBounds() or view.scene.updateBounds()
or parentMaxZ or this combined with the update functions but I got no
change =\

How can I really update these values?

Thank you in advance =)