Height is always changed/apperas different in almost every scan/manga, (we clearly see Beefcake dwafing Skyscrapers, the we see Beefcake not ebing that much bigger than Saitama etc). its either beefcake is the size of a large construct like you said? OR beefcake is around 12km tall:
Using common sense, i think we can both agree its the latter, right?
The vast majority of panels show Beefcake not being that much bigger than buildings. One of the major plot points was him getting on one knee, swinging his arm in a similar motion to someone throwing a backhand, which resulted in buildings being knocked down. If he was 12km tall, roughly the standard cruising altitude for most jet airliners, he would be far too tall to knock down buildings with a backhand just by getting on one knee. I think common sense, along with consistent portrayal, doesn't agree with him being anywhere near that tall.
Theres a difference in our gis, Mine shows an explosion, while yours shows a flash of light.
i can light an 10trillion wat Ligt bulb and itll be visible from space.
I can set off 100nukes and it would also be visible from space
you see how different those two examples are?
Nuclear explosions can be seen in space too and they don't encompass anywhere near the area of a multiple countries.
All in all, it seems very sketchy to conclude the OPM cities are the size of countries based on information in the manga.
But I doubt we'll come to a consensus on this point, so we can just agree to disagree.