Shrink and Crop a UIPickerView in iOS4

Question

How do you shrink a UIPickerView in iOS4?
Nothing works for me:
- Changing the frame value in the .xib as text - Setting the frame

I can shrink using a transform, but I want to hide the background and see only 3 or 1 rows.

Yes, this question has been asked before .. http://stackoverflow.com/questions/3209895/catransition-how-to-clip-to-bounds-of-uiview

I also tried to hide subviews but there were none (returned NULL).

[(UIView*)[[myPickerView subviews] objectAtIndex:0] setHidden:YES];
[(UIView*)[[myPickerView subviews] objectAtIndex:10] setHidden:YES];