I was revisiting included painting schemes and a decal sheet and I've come to conclusion that 1) I don't like the decals (printing quality), so I need to make masks, and 2) I would like to have some other camouflage rather than yellow/dark green/dark earth. After some research I've found this African P2399 of 451 Sqn, RAAF in the desert scheme. I've found only this one photo.

Also, RS Models gives this as one of the option for their Magister in 1/72 scale:

If I will manage to cut masks with my cutter I will go with this P2399. There should have been a standard for the numbers – size of the symbols, etc. It would be great if somebody can give me a reference to it. Also, I'm wondering about the number on the rudder and on the lower wing surfaces – should I add it there as well?

@fiveten That's the backup plan if I wouldn't get any other information. The only thing I would expect is some rules/standards for the serials. From other hand I do believe that this aircraft was repaint at field, so personel may not follow all of the rules. Anyway, if I wouldn't get anything I will use RS interpretation.

Interesting photo, thanks Spiros!

Thank you, John! @johnb

I've spent this day for sanding and re-scribing panel lines. Black areas on the fuselage and wings is CA putty.

RAF serial numbers are 12 inches high, Dmitry. The underwing serials would be 24 or 36 inches.

Good progress, Dmitry @starfar
For sure you will solve those gaps nicely.

@tcinla Thank you, Tom. This results in ~10mm in this scale, so I have some chances with my cutter.

Spiros (@fiveten), John (@johnb), George (@gblair) – thank you, mates!

I've decided to check CA-filled surfaces before the further assembly. I've sprayed Mr. Surfacer 1500, fixed some small issues, sprayed again and polished that surfaces afterwards. Now I can proceed with other parts like engine and cowling.

Also, I forgot to mention it previously, originally the kit doesn't show the line between flaps on each wing.