This I-16 was obtained from the Hasegawa type 24 kit, 1/72.
This model has some good characteristics, as the clean moulding and pleasant building up, but it has some heavy defects too.
The most visible defect is the wing platform, that is a bit too rastremated, even if not as strongly as on the older Revell kit. As a result, the wings appear a bit too pointed.
One can choose to ignore this, but I preferred to correct the problem. I had to:

carefully remove the ailerons; cut a piece of rear wing edge from the upper wing half, then glue it moved back on the lower half; glue plasticard on the remaining space; add stripes of plasticard on the back of the aileron recess; glue with cyanoacrilate, fill with nitro putty mixed to cyanoacrilate; reshape accurately, recover details, rejoint ailerons.

The main wheel bay is too flat, it has to be opened; a new bottom will be added with plasticard, glued and painted with a thick layer of paint in such way to be filleted to the sidewalls; a nervure and a small hole will be the only details required.
The landing gear doors have to be thinned, and their nervures built with sprue.
The exhaust stacks are not too satisfying, I preferred to remove them, drill the fuselage and install new pipes made by plastic tube. The upper left and both lower recesses have two pipes each, the other recessed have only one pipe.
The air outlet of the oil radiator under the nose has to be modified; it should have a strongly oblique outlet.
Some details of the cockpit have to be added, the gunsight in particular.
The guns and Venturi holes were made by a small drill tool.
The pitot can be replaced by a metallic probe to increase strength.
The attachments for the camera gun have to be added on the fuselage back.

Well, these are the works required by building the model as the same version given on the box (nominally type 24).
But I decided to build my model as a type 29, the last type in production.
The required works were:

• to modify the front plate with a new UBS hole in central/lower position; the air intake is moved on the right side (two configurtions are possible), and a small outlet is on the right side of the nose;
• there is the UBS fairing under the nose; it extends between the landing gear bays.
• The bays have to be slightly moved outwards (an easy work to do by grinding, when the bottom is removed), and, in my opinion, they have not a fully circolar shape, but are slightly flattened in correspondace to the UBS fairing (but this is a my interpretation of photos, not a sure fact);
• the landing gear should be shortened of 0,4 mm (but none will complain if you leave it as it is);
• the prop blades have to be shortened of 1 mm each;
• the wing guns (and, probably, the waste cartridge outlet slots) have to be removed;
• the scratchbuilt rocket rails have to be added;
• a large antenna mast and an antenna wire were added on the right side.
• The main sources utilized were

The aircraft chosen is reproduced on the photo below; it  belongs to the Moscow PVO; the pilots are the sergeant Slesarchuck, Gosin and Pererva. Its camouflage looks AII green and black; the outlines are hard. Note that the green paint fades more quickly on metallic parts (this was observed on many I-16s and MiG-3s), so the fabric-covered stabilizer gives the idea to be painted of a darker and different color, but probably it is unfaded AII green.  However, none will ever demonstrate that it was not blue or whatever color you prefer. The prop blades appear field repainted on this aircraft, probably green. They usually were natural metal on most I-16s, eventually with their back painted black. The slogan za....? is sadly hidden on the photo; so, I preferred to omit it, giving a likely reproduction of the aircraft before its painting.

The decals are from scrap, and the red star on the spinner was painted by brush.
The painting technique was by hand brush, with panel lines darkened with a mix of acrilic black, alcohol and gloss trasparent. Some drybrushing was made on the details of the landing gear and the cockpit. The metallic parts were painted with a slightly lighter shade of green.
 

Main references for this model:
Polikarpov I-16 fighter, Y.Gordon and K.Dexter
Polikarpov fighters in actions, by Hans-Heiri Stapfer
http://vvs.hobbyvista.com/Markings/I16/type29/index.php
http://vvs.hobbyvista.com/ModelArticles/I-16/index.php
http://vvs.hobbyvista.com/ModelReviews/Airwaves/I16T29/index.php
http://www.airwarfareforum.com/viewtopic.php?t=3024