I know this is an old topic, but here's another hack that might help.
Create labels for the column headings above the Gallery. For each label use calculated values for the x position and the width to match the Gallery item so:
For the label width: MyGalleryItem.Width
For the label x position: MyGallery.X + MyGalleryItem.X
This will cause the label width and alignment to always match the field for which it's the heading. It's a bit of a faff, but worth it in the long run.
The other more obvious alternative if you want a pure data table is to use the 'Data Table' control, which does all this for you. However, as far as I can see this doesn't support custom layouts. e.g. in my case I needed a second row for a description that spanned multiple columns in the first row.