MiG-21MF vs MiG-21bis nose difference

[Laurent]

Hello.

For the guys who aren't scale modellers, let me tell you that there's been a little revolution recently: Eduard Models has released an 1/48 accurate MiG-21MF model. They are planning to make a MiG-21bis but the release has been delayed because modellers have warned them that the bis nose is different from the MF nose. They went to Berlin to make measurements on a real MiG-21bis (initially, they took a Riga "MiG-21ST" for reference) and the result is given in their latest newsletter:

Behind the stainless intake ring,
there is a diameter difference of 22mm, with
the ‘BIS’ being bigger. No big wup, in scale, that
amounts to about 0.4mm. What’s worse, though,
is that an approximately 15cm section of the
nose has a different shape, the transformation
from a circular section to an elliptical takes on
a different form, period. So, we are conducting
the relevant changes.

A French colleague overlayed...

... to...

... and the result is...

It is clearly visible that the bis nose is a little shorter so the intake is wider. Is there another difference ? Do you know what Eduard means when they say "that an approximately 15cm section of the nose has a different shape, the transformation from a circular section to an elliptical takes on a different form" ? Help would be appreciated.
Cheers !

Laurent

[Karrahahu1]

Do you know what Eduard means when they say "that an approximately 15cm section of the nose has a different shape,???