ummm. 1 month later and the op still hasn't updated the DIY?
This mod may reduce horizontal flex, but there will still be flex on the vertical plane, diagonal plane, etc.. You do tie 2 points together, but now they will move in unison.
Triangulation seems to be the key factor to really improve the effectiveness of bracing.
You can add a B and C pillar bar, as in the picture in this thread. They will reduce the horizontal flex. But, add a 3rd bar from the B pillar to the C pillar -- Triangulate -- and now you have a much more solid structure that will reduce flex much more.
I'm sure there is a lot more to it, but from the little bits of info I have read, including sites dedicated to road racing, triangulation should be used.