myy passenger seat mount was rusted to shit... and the little bit of floor underneath, so I ct it out to weld a new piece in... in doing so, I cut a section out of the brace that runs right underneath that mount(the small one under the outside mounts)

di I screw up? or can I just weld some 1"x 14ga (or 1/8") in the place of that gap and do the little piece of the pan and the brace over that?

is that even needed? would just doubling up the floor pan there suffice?

to illustrate:
I cut at the red line here...

The main purpose of that reinforcement is to prevent the floor from bouncing or acting like a can that pops in and out when under certain pressure. I think you'll be OK with what is left, I would still try and make something similar to replace the thing, it's not that complicated.

yea, I can either reinforce it with extra welds or put a stip of 1"x1/8" steel there... I played with it tonight and think it will be ok