I'm not a big fan of juju either, but a good glob of spooge goes a long way.

No input on the numbers, but I am a little confused by the location of the bracing in your truss. When we design a king post truss, the braces join the midspan of the rafters to the base of the kingpost. The typical layout is running the barce parallel to the opposing roof pitch. The trick is to allow sufficient wood beyond the brace to resist shear.

This arrangement keeps the force in the brace from pushing down on the bottom chord. It is also what is typical in historic trusses. In my opinion it's the correct layout and allows the chord to work purely in tension (other than it's own weight).

There are even king post trusses in existance that have no connection at all between the kingpost and the bottom chord. These and other historic trusses seem to only get in trouble when a ceiling load is added. Which is why i'm a little concerned about your bracing settup.