I must comment, that your eye strain over a day of large format photography, and the accuracy of focus, may suffer with loups for focusing above 5x. The higher magnification loups began to magnify the ground glass grind and/or the fresnel texture. This annoys your eyes, and can cause visual fatigue.

Years ago a Photo magazine published a test of film holders and threw out excellent holders, when the issue was the test procedure and a 20X magnifier...

We tested these same holders ourselves against ANSI standards, the article was quite often in error.