In case this is useful to anyone, I added additional verses (even) to the Brumel 'O crux, ave' for use alternatim with the hymn 'Vexilla regis', and updated the text underlay in a way that seemed more probable to me based on one of the mss. of the piece and the alignment with the plainchant melody.
Hopefully someone gets some mileage out of it! We're singing it on Sunday for Vespers.
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