I'm confused, as far as I can see you've indeed cut birds mouths at both ends, and there's no purlin to need one. Those horizontal ties near the top is presumably triangulation to keep the steel in place until the gable wall is built, and the cross bracing between the first 3 rafters at the same height to keep everything in line?
Architect swallowed the belt and braces book. Had to put brick tor in the block beds and straps across the rafter tops linking them together at the ridge.
Bonkers.
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