Sencha Touch's loadmask customization

Sencha Touch's loadmask customization

Is there any way to customize the loadmask properties without needing to
create a new one? I want to increase the size of the darker grey box (i
think its the inner-mask right?) because i want to use html to make the
loadmask looks better. But with box that has a size like that, there's
little thing that you can do to make the loadmask looks better.
masked: {
xtype: 'loadmask',
message: 'Now Loading..',
}
How would i set that darker grey box size? I tried with height and width
but that one modifies the whole loadmask size, not the darker grey box
area.