Rendering of QSpacerItem in Gridlayout

[Needy]

I am making a Designer. Where i am using QGridLayout.
Initial Approach: I extended a QWidget and i used to paint this widget when dropped in QGridLayout. Then using Stretch i used to make it look bigger then any other row/ column. And also when i used to drop spacer. I used to change stretch of all other row/ column to 1, and row/ column that contains stretch to 2. So to give a feeling of spacer(looks larger than other).

Problem: Now i allow user to change Stretch manually. Because of which my spacer looks small when other rows are stretched.

Looking For: Please give your suggestion on how should i proceed with this problem.

Thanks in Advance