Populate Sharepoint List With data in it (List Definition) in site definition

Question

Hi everybody,

I have a list and I want to populate this List with data in it. I want to do it via WSPBuilder as a feature. I tried to populate it within in the Elements.xml file, But I got the data not nested inside each other, as my list contains items inside a folders

Folder1
 |
 |__Item1
 |__Item2

Folder2
 |
 |__Item1

so I wanted to populate the list to be like the Above Figure but instead I get them all in the same level, I guess the problem is I have to set the folderRef for each element as I think.

So could you please tell me if I'm right or wrong, and if there is a better way from performance wise?

Thanks

Any Help Please !!!!