Thanks Andy. I had some confusion over this, which was addressed by another user at DW1000 PCB Design - RF Transmission Line Length - #4 by FIRSTDRAGON. Is the data sheet wrong or should I just make them as short as possible?
And thanks for the advice with materials. As before, my prototype was built on FR4 but the track widths were designed for RO4350B so hopefully there will be a performance improvement with changes to these dimensions.