I did some more research myself and wanted to post what I have found.
Short answer: Static longitudinal stability does not require download on the tail.
After reading quiet flyer's comment, I wasn't sure if there was zero difference in incidence between stabilizers and wings of a plane which uses outboard horizontal stabilizers and the drawings in the paper which I've found the ohs image I added to the question looked like they had parallel flight surfaces but I wasn't sure if they were original drawings which they made the tests with.
So I designed and built this small guy which has parallel flight surfaces to be sure.
I started testing by placing CoG somewhere around here.
which caused it to immediately pitch down after hand launching it
I removed weight from the tip until none was left and CoG was shifted all the way to the back of the trailing edge like this, and finally it flew very good at this CoG location.
After searching for "center of gravity" in the paper which I took the OHS image in the question from I found this;
After some more research I came across this which answers my question.