Control's Transparency

Hello,

I am developong an app with a form that has background image. The form
contains standard controls (TCheckBox, TRadioButton), and they must be
transparent. I have tried:
1) Setting WS_EX_TRANSPARENT flag in CreateParams()
2) Adding csOpaque to ControlStyle
3) Setting Brush->Style to bsClear
4) Supressing WM_ERASEBKGND message
and some more millions of variants.
Nothing helps, most results in unpredictable painting.

Shall I write my own checkbox from scratch, or, nevertheless, there is more
productive method?

Thank you.