how do the russians do their rib stitching?

the items in question are the tailfeathers of a 4 seat radial engined
Yak. (yak 18T I think it is)

we're not sure whether we are following original factory work or
someones abortion.

the rib caps have a section like ----v----
in the centre of the v there is a hole every inch.
it appears that instead of following english/american practise of
tying the ribstitch around the rib from top to bottom and tying off
each loop individually the ruskies have taken two adjoining holes and
stitched button style around and around, then moved to the next pair
and stitched around and around and so on.
the top stitching is only along the top rib cap.
the bottom rib stitching is only along the bottom rib cap.

are we looking at factory original stitching or is this something that
subsequent refabric work has done?

if it is the original ruskie system it produces a very neat rib
treatment.

Stealth Pilot