[El Gato]

The North Koreans adapted them to carry heavier payloads.

For much the same reason that the first generation or three of Soviet missiles were brutes, because their nuclear warheads were so huge. Ours were too, but other than the B-36, we put our effort into smaller warheads, not larger platforms to carry them.

The NK nukes, or any Iranian ones, are likely to be somewhat crude, and quite heavy.

[familyop]

" The NK nukes, or any Iranian ones, are likely to be somewhat crude, and quite heavy."

...if we can believe that the N. Korean shot of a few months ago was really a "dud" instead of a light yield. The test facility was designed by the Russians with baffles for concealment of fallout.