Subframe connectors question

I had a similar issue with homemade subframe connectors made of 2" x 3" box tubing. I ended up putting a jack under the back end of the connectors and pushing them up flush against the rear frame rails before I welded them in. In my mind once they're welded in and the jack is let down it puts a constant tension on the connectors to kind of "pull" the front and rear subframes together. I do have a slight raised area in the floor in front of the back seat now but it's barely noticeable unless you're looking for it.