Your talking about 50 microns or 2 thou in old money. I doubt that either LN or LV have their castings stress relieved for this plane, so after machining they can move as that tolerance for the application perfectly acceptable. Most router planes get a large wooden base screwed into them which I’m sure will have been planned down to less than 50 microns flatness, equally the surface it’s being used on to register to it will definitely be less than 50 microns flatness especially if it’s been standing a few hours / over night. Ok that’s all tongue in cheek, to try to highlight that it’s only usually in metalwork we’re 50 microns can become an issue.
As an aside, I found that the LN castings on some planes I’ve worked with have been as soft as soap. Had to have one of my own planes replaced because of it.
I don’t have the same opinion as Derek, I believe that if there had been a design right filed on the shape of these planes, both LV and LN would be in breach……there both in my opinion just tweaked copies of the Stanley / Record, so its a free for all, open season for anyone to manufacture of the same style. The one thing I’ve found with both LN and LV is their customer back up has been outstanding and their stuff holds it’s value.