Welcome Matthew:

This site is a trove of ideas, some better than others. See the Mews Picture thread under the Facilities/Mews/Equipment section.

Two things I would suggest is to attach the weathering yard to the mews with the mews entrance through the weathering yard. This functions as a double door for the mews in case the bird somehow gets loose in the mews.

Second is to have the perch at a height so the hawk's eyes are the same level as yours. Passage birds especially do not like to be on the ground when you enter the space.

Best wishes for success,
John