GuiScrollCtrl - ignores changes in profile's bitmap ?

I have a guiScrollCtrl and would like to change the bitmap for the widgets,
is there a trick ?

It's taking the rest of the new profile values (eg Border),
but seems to be ignoring the bitmap parameter.

here's the setup,
tia for any advice.

i'd love it if i was just missing something and didn't have to get involved in the engine..

the profiles

new GuiControlProfile(MyScrollProfile)
{
   bitmap = "./myScroll";
   border = 2;         // just to have some diff. besides bitmap.
};

new GuiControlProfile(MyScrollDimProfile)
{
   bitmap = "./myScroll_dim";
   border = 0;         // just to have some diff. besides bitmap.
};

the scroll control

new GuiScrollCtrl(myScroll) {
         profile = "MyScrollProfile";
         horizSizing = "width";
         vertSizing = "relative";
         position = "3 12";
         extent = "220 121";
         minExtent = "8 8";
         visible = "1";
         willFirstRespond = "1";
         hScrollBar = "alwaysOff";
         vScrollBar = "dynamic";
         constantThumbHeight = "0";
         childMargin = "0 0";
         helpTag = "0";

Switching profiles

if(%val)
   myScroll.setProfile(MyScrollProfile);
else
   myScroll.setProfile(MyScrollDimProfile);