Technically sound, handling with weaknesses

I bought this unit because of the good test results with respect to accuracy. After parallel measurements with a conventional BMG (these old things uses the physician, with a hand pump and earplugs) we can confirm the accuracy.
Too bad, I find that the collar does not fit perfectly, it does not sit well because the arm that is not up and down the same thickness, but is slightly conical.
For my husband, we had to buy the XL-cuff (under 30), although he is not now the mega-packers, but normally has strong men arms. With a little skill but fit at least two collars in the pocket. (For me, the XL-cuff is unfortunately too great, although I'm a little weight training. So we actually need two cuffs.)
The ON / OFF switch is in our view an unfavorable position, because you can not see him. One can feel for him though good, but do not know on what position he is and therefore must always tilt the unit to investigate. I have glued myself a little red and green dot at the top of, for orientation.