Hello Rick,
When i did my rails the rot carried forward to include the jack pickup point,i had to remove 22 inches of the sill to reach the point where the chassis rail /sill / crossmember meet in order to eliminate all the corrosion in that area,(this was done on both sides).
The repair sections did not carry forward enough and i had to make my own.
It is probable too late, but if not, open up the sill to ensure the corrosion has not gone too far forward.
To clarify, cut a section out at the sill end to inspect ,if everything is OK it is easy to weld in a new end section.
If the rot has carried forward you will have to remove a section of sill ,the jacking point. Weld in new metal,repair the old jacking point and re weld it into position.
With the outer sill section i made a template and had a new piece made out of the same thickness of metal.