The only thing I have a bit of a problem with is where you put the metal angle brackets. The photo shows that...if I'm reading the photo right... that you put them on the same side as the canvas.
The possible problem I see is that if for some reason they start to rust due to humidity, they could stain the canvas. Odds are that they are below the lip of the wood so they aren't actually touching the canvas but still something to consider.
I have opened up frame jobs where the driver points are all rusted from the humidity where they were hung.
Now... for this job, where it is going into a fairly climate controlled building, it might not ever be a problem but if this was going into someones house where the humidity could fluctuate easily, it might show up in the future.
Just something to think about for the future jobs.
Of course, if we are going to talk about all that "archival stuff" ..the strainer wood needs to be sealed before the canvas is stretched so the acids of the wood don't eat at the fabric.
Too bad you couldn't convince them to put a nice, large frame around it!!