as to the span of the "truss" (how far apart the walls are) and what is the spacing of the rafters - 16 inch or 24 inch centers, it is hard to make a judgement.
But, it sounds like overkill with the doubling of the rafters unless you have a long span. The tying of the rafters together with the 2x6 about 1/2 way up is good. I assume you are wanting to keep the ceiling high, and that is why 1/2 way up instead of level with the top of the walls.
Instead of bolts, I would use 3 inch decking screws, and with the 2x6 "ties" I would also use some PL400 in addition to the screws.
Not sure what you mean by hanging drywall above/below the truss.