I didn't write that to scare anyone out of tackling some welding. I was just pointing out that it would take more time and involve having to cut out and redo the spot welds, etc. More of a PITA than drilling a few holes and putting in what likely would be the same weight X rods. Which the X rods may get you closer to your goal of reducing flex. I do think if you welded the bracing in, it would be stronger than the X rods. But at least you have several options. It just depends on how far you want to go.
or just buy a GP.....