I've got some bad rot I'm going to weld up behind the beam pad where the isolator goes.

Essentially I want to replace from the bolt hole to the upsweep curve. No biggie, I had planned this. Well I have to since there is no steel around half the pad/bolt hole for the isolator/bushing! My question is though how thick of steel was there stock? Not much left for me to go by!

Better to weld in one plate or two thinner ones? I can see some 12 gauge doubled up and gusseted looking quite habdy.