Galvo scale seems to warp toward edges on large lenses

I have meticulously followed the instructions in the Lightburn lens correction guide video for a 70, 110,174 and 300mm lenses. However on the 300mm lens the scale is either accurate on a large square or a small one but not both. if I scale using a 300mm square then a small 100mm square is innacurate by a couple of mm. If I precisely scale a 100mm square, a 200mm square is fractionally innacurate (1/2 mm), but a 300mm square then comes out at 304mm. Trapezoid, skew and bulge all seem fine at all settings. I have drawn the conclusion (maybe erroneously) that the scale starts to warp/distort/stretch as it approaches the edge of the field and there seems no way to get around that. Has anyone else encountered this and found any kind of a solution?

Are you adjusting the lens corrections?

My F420mm came with factory adjustments. My F254, I followed the Lightburn correction videos and the remaining two with the software for lens correction that came with EZCad2, Corfile.

Corefile is easier to use and substantially quicker than the manual method, you have to have a windows machine to run it. That wouldn’t be an issue it looks like…

I do know that many get distortion at or near the coverage area.

Did you get these with the machine?

Usually the vendor generates the correction files…

Good luck…