I'm framing out all the interior rooms inside a rectangular truss roof house. The walls interlock with one another and form an independent structure underneath the trusses, and connect to the outside wall frames. It's all very strong, but the longer sections of walls are up to around 3.6m, and there's a bit more lateral flexing at the top of the walls then I would like. Normally these would be attached to trusses with a movable bracket, but the problem is that these run parallel to the trusses, and the bottom chords of the trusses are thinner and have much more flex then the walls themselves making them useless as a reinforcement point.

The trusses originally had thin batten wood on the underside for attaching the ceiling plasterboard. This would have given them lateral strength by tying the trusses to the outside walls of the frame.

Now I am thinking that I should run lengths of wood along the tops of the internal walls, over the tops of the bottom chords of the trusses and not connected to them. These would run the length of the house and provide lateral strength to the walls, but also provide a much stronger and more stable framing spot to hang furring channels for the plasterboard. This solution would be far stronger than the original build where the ceiling was hung from the wimpy trusses.

Though I'm not sure what to describe these as, therefore what standard they should meet. I'm imagining that they will support the weight of a person if you need to get up in the ceiling and walk around for electrical work etc, but beyond that all they're supporting is the plasterboard in the middle of the rooms. The max span is going to be around 3m max, generally less than 2.6m. The wood I have on hand is 90x45mm MGP10.