Is there a way to tweak the amount of padding inside UI elements in Ubuntu, besides installing a different gtk theme?

This is how eclipse looks in Ubuntu (with the Radiance theme)

![Crop of eclipse in Ubuntu](https://i.stack.imgur.com/dzLVf.png)

And this is how it looks on XP

![Crop of eclipse in Windows Xp](https://i.stack.imgur.com/xMf2Z.png)

What I would like to do is reduce the padding around the icons in the toolbar or the padding around text in tabs. Is there an app or some config file I could edit?