The second link just goes to a master index. As I don’t read Cryllic, and you never mentioned the nation of origin, it took me a while to find the entry.

Yugoslavia, eh?

I question the attributed 1940 quote from Igor Sikorsky, in that it is doubtful that 2x820hp engines (1,640 hp total) could produce a higher speed than the XP-38 (which had reached 413 mph in 1939 with 2×1,090 hp engines {2,180 hp total}).

It might be able, through its better aerodynamics, to match the BF-110C (which reached 348 mph by 1939 with 2×1,085 hp engines {2,170 hp total}).

The IK-5 with the Hispano-Suisa H.38 39 had 32% less installed power than either of those.

If the DB601 Aa (1,085 hp each) had been installed, it might well have given the P-38 a good fight (speed-wise), but we’ll never know, just as its maneuverability & other performance is unknown.

An interesting aircraft, though… nice find.