Raising garage roof on prefab concrete garage

Hello

Feel free to shoot me down if you think my plan is at all dangerous or stupid.
I am planning on getting my old asbestos garage roof removed professionally and then installing a new one myself.
My thoughts are however in the process it would be nice to raise the whole roof structure up by a couple inches.
I was planning on therefore putting some 2x4 on top of the sections securing it, and then I was going to lift the rafters and rebolt them in the holes that are slightly lower down.
My issue is the back of the garage does not have these convenient holes so I was planning on using something like this to extend the metal frame down slightly.
Any input definitely appreciated.

Those might be a bit flimsy, as you are going from angle (stronger) to flat. Perhaps you could use a short length of box section or angle iron, bolted to the inside of the truss end plate, and extending down.

Instead of 2x4, perhaps you could use a concrete gravel board, carefully drilled to accept a bracket.
Sit on top of existing wall and butt it up against the truss end, with small plates fixed top and bottom, to stop it falling outwards.

Yeah good point I think I will use some box section.
Attach the boards to the concrete with box section then attach the roof trusses to the boards with the original struts saving the need for extension.