Welding anything is a choice, if you reinforce it to much it will not flex and absorb shocks as it was designed. Then it breaks something else, because the shock load is still there it is just transfered. I have welded quite a few frames on class eight trucks, and never fish plated them, never had one break either. The most common fault people do is they want the weld to look good so the end up grinding the frame away, You are welding the crack, gouge it out, fit it, do not overheat it, that means chip it clean and spray with a water bottle, I use to use an air chisel with a shortened flat blade to chip and stress relieve the weld, clean with a wire brush, then weld again, clamp scrap steel to the other side to keep in place, and act as a heat sink. Then grind the back side clean, and weld that up. You have to set your heat and speed so you do not undercut. I was never into grinding the weld off, unless it was an area that had anouther piece bolted to it, then only where it overlaps.
Just a thought!