i use thin cardboard that wrapped around the tube more then once so i could line it up straight then placed my new insert in nipped the top nut so that it held it square then tacked it together then removed to fully weld my new inserts were a firm fit in the tube . i would be carefull about welding them down to far as that makes it hard to die grind any excess weld u make get inside the tube preventing the installation of your new insert . i have done 5 sets this way and have never had a problem ,so have fun