Yup but if it was factory or certified it's fine.
Back in the day I was a good enough welder to do a little of that stuff (with caveats I wont go into here). We wouldnt do anything without engineers support.
That included putting bigger hinge pivots on for tubs (something like 2" diameter with applicable new bosses of over original 1-3/4"). Something like that, plus back chassis frames for ringfeder etc.
Again always with engineers support and from memory laminated chassis were another thing altgether
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