.scale_x and .size_x can resize your panel.
Scale will scale it down or up, size will clip or repeat your bmap image over the resized panel.
in atypes.h you can find all the attributes of every object.
May come in handy (sure did for me when I found out

).
Code:
typedef struct PANEL {
...
var scale_x,scale_y;
var size_x,size_y; // panel dimension
...
}