Hopefully this will cheer you up a little.
That style stringer setup above were the old style (pre - 1972??) and were just hollow shells by design. Feel free to look at the patent if you don't beleive me. They are built that way and one of the best and strongest features of the seacraft. Oceanmaster and many other boat builders still use this stringer design today.
The 1972 and later stringers are 2 bigger box stringers filled with foam. Stringers don't ROT in any seacraft (except the very very old early early 1960's boats) when they used wood.
Here's the post 1972 stringer style.
The Center stringer in the older boats was wood and laster was replaced using PVC?? or some other type of half round tube.