Early A Floor Pan Stress Cracks

I have found that the floor pan around the bolt holes for the driver's seat is cracked due to the flexing of the seat.

I am going to re-weld the crack but have been scratching my head on how to re-enforce the floor to prevent future cracking. I have thought that if I put down another plate and weld it in it would just move the stress crack to another location.

Any ideas or suggestions on how other have addressed this would be appreciated.

Jesse