"....looks like the arm doesnt need it, the counterwheight is in the middle when I set up this cartridge."
The purpose of the added weight has naught to do with VTF, but with tweaking the arm resonance relative to the dynamic compliance of the cart suspension. Since the DL103 is a relatively low compliance cart (though, as I said, not as low as it's specs makes it appear), you may see sonic upgrades by adding the weight (and readjusting the arm for correct VTF). At this point, however, if you've got the rig running, just enjoy some music. You'll want to establish a listening reference point before you make any changes, or do any experimenting. Though, were I you, I'd lower that VTF to 2.5 at some early point.
If you do want to experiment with adding weight to the headshell, and you've got an electronic scale, I'd suggest weighing out a blob of Blu-Tac and attaching it to the top of the headshell. That way, you don't have to remove/readjust the cart while you're experimenting. If you like the change, you can add the VPI weight for Handsome Good Looks.
And btw, congratulations on getting 'er going.