Tying the rear frame rails together? Opinions please!!!

Yea I was doing research and yes not paying for a full frame and then have to modify a 10k frame to fit dart or pay twice that for frame that is fitted to the dart. I have a shell sitting in garage :) so want to get all the welding out of the way now before it's put back together. Was hoping someone has done this or may give further advice if it's worth the work, obviously more metal supports the more ridged it will become.