I have only seen it done and tried myself with an inadequate welder. I do not know where precut plates are available but they used to be available for '28-'32 but tube frames are so common today I have not seen the plates advertised lately, so you may have to cut your own. I can only make one suggestion. You can choose to weld slightly inside the frame (preferred) or flush to the outside of the top and bottom of the frame. The second way has the disadvantage that when you grind the welds for appearance you weaken the weld so it is better to set the plates in about 1/8" and weld inside the edge. I wish I had a MIG welder, go to it!

Don Shillady
Retired Scientist/teen rodder