frame cap?

my frame rails are bad in the down on the bottoms just before the leaf mounts, im doing the frame connectors into the original frame rails through the floors and doing the leaf spring relocation as well, my question is will capping the sections in concern with a safe-t-cap style thing work, or should i do it myself with 16 gauge sheet metal. im more worried about strength over looks, can make it look pretty later.

Thanks,
steve