I have met Stuart a few times and I have great respect for him regarding his knowledge of riflescopes. I also appreciate his thoughts on the 5-52X56 HM. If my memory is correct, I believe he didn't like the fact this scope has huge range of elevation adjustment but that the IQ will start to suffer when you get to the extreme in elevation and you have to adjust the side focus more to compensate. If my memory is incorrect, I blame advancing age, society and global warming.
It is my understanding this degradation of IQ and need to fiddle with the side focus more, will occur with any scope when it gets to such adjustment ranges but then again, the vast majority of scopes can't even get anywhere near those numbers. Add to this, the wide angle eyepiece with its wider view than a regular riflescope.
March has this page in their support area, about this very situation:
How-to-adjust-5-42.pdf (marchscopes.com)
The 5-42X56 has 140 MOA (40 MIL) of adjustment range, whereas the other March scopes with similar 34mm tubes have about 60 MOA (17MIL).
If you intend to spend a lot of time at the edge of adjustment with a 5-42X56, you should really use a canted rail and step down from the extreme setting. I always strive to stay as near the center of the range for the very best IQ. So in my March-X 10-60X56 HM installed on my F-TR rifle, I have it set with a combination of 20MOA canted rail and Burris XTR rings to have it very close to center for 1000 yard zero, where this rifle is used 95% of the time.