According to page 6 of the 20x30 1 1/2 the "interior 2x6 is sistered to truss after roof is on." So my question is what is a good method to make sure all the trusses are aligned side to side since I don't have a flat section to sit on the top plate like there would be with a birds mouth cut into the rafter.
The way I envisioned that being built the vent block spacing is set by the H10 bracket that connects the wall plates, the vent block and the outer 2x6 of the site built truss. The inside joint gusset and the 11x11 tie gusset can be put on after the interior 2x6 is installed. The roof can then be sheathed and roofing installed.
I'm not sure that we're on the same page here. What I mean is, if a truss is slightly high on one side then it will be low on the other and as you move along if there are slight variations from truss to truss there will be a ripple or wave along the length of the roof.
It often works better if you have the trusses done by a local truss company. They will engineer it for the local loads and can probably address the question you mention.