welding trans crossmember

I am wanting to add a scallop to the other side of the crossmember so the dual exhaust will tuck up nicely. I have an extra crossmember. should I cutout a scallop then weld in some material or cut em both in two & weld the 2 good halves together and should I have it mounted in place for dead on alignment when I weld. what do you guys think? thank you for your time. RR
I'd recommend cutting the bolt-in crossmember (out of the car), then bolting it up and using it to mark where to cut the torsion bar crossmemeber on the car. Then take the bolt-in crossmember out and box it back up and cut the torsion bar crossmember and box it up.