This evening I did some measuring on the sub floor panel. It looks like the forward most stiffener needs to be 6 1/2 inches long whereas the aft most stiffener needs to be 7 inches long. Since there are five stiffeners for each floor panel, that makes it easy...just add 1/8 inch to each successive one. Here they are after shearing.

...the first bend.

...and the other two bends.

Although these came out great, it seems like there's always something that can be done better. In this case, I forgot to debur them before bending. No big deal...just took longer to get the edges cleaned up.