This topic interests me as well. I appreciate the call for an engineer, I also like to understand what is going on.
Let me try an example.
A 24' kingpost truss with 12/12 pitch, 10000 lb combined load and bottom chord at the plate. I come up with ~3750 lbs tension at the spline and ~5300 lbs compression at the heel joint.
If I raise the bottom chord do the forces increase as a proportion of height the chord is raised up the king? In other words, if the tie moves up 1/4 the height of the king does the tension increase by 25%?
