There is nothing wrong with re-arching if done properly, which means annealing, straightening, re-forming, then re-heat treating and of course...NDT, as in Mag Particle Inspection.
The gear legs are most likely 6150 Carbon Steel and heat treated to either 150-170ksi, or 160-180 ksi. Since they've sagged in laymem terms...I'd call that "yielded" so to work harden them further, by over-bending in the opposite direction...simply put, you're risking real money, over chump change.
If it were me, I'd follow the advice of many and go to an approved, knowledgeable, reputable source...that's what you pay for in this game. Knowledge and skill.
(although maybe it'd work to drive a pickup over them, with the ends on a couple 4x4's till you're happy)
S.