Very interesting document, thank you. The quality make me think about the Fokker Found's standard.
I've found some more pictures this week-end.
From "Soviet Combat Aircraft of the WW2" - Vol.1, Single-Engined Fighters - by Yefim Gordon Dmitri Khazanov.
-2 views of the 5th B-1 fitted with retractable ski landing gear.
-Front view of the first I-26 prototype made by Yakovlev.
-Nice picture of the SK-2 prototype. This elegant aircraft was a creation of Matus Bisnovat.
The first prototype had a closed "buried" cockpit with 2 position modes, flight and landing/take off with a retractable windscreen !
-Front view of the Yak-1 (No 3855) in snow camouflage displayed on page 2, this Yak was used to test ski landing gear undercarriage.
Note the 6x RS-82 rockets.
-Interesting profile photo of a Yak-7V convertion trainer. Undercarriage bay was partially faired over.
More commun now, from Squadron Signal Publication - Petlyakov Pe-2.
Close view of the skis of the Pe-2 serie 11 presented by Microw on page 2, note the shape of the skis used as landing gear bay door.
Another view of the Pe-2 serie 1 presented by Wurger, the retractable tail ski is more visible on it.
Enjoy.