[Graham Boak]

My comment on sealants was thinking particularly of oil seals in the lubrication system and the engine, and directed at the "leakiness" of the engine rather than its performance. Most if not all of the criticism I've seen about the Ha 40 has been about its reliability, not any lack of power when it was working. So whereas the performance of any one Hien was unlikely to benefit from an original DB601, the performance of the Hien force as a whole could be another matter.

As for the design of the Hien compared to the Bf10F or the MC 202, it appears to have a large wing and so a larger surface area, giving an increase in skin friction drag (probably further increased by lower build standards) and therefore lower top speed. This would be balanced by lower lift-induced drag (at the same weight) with better performance at altitude, better turning at low speeds. It might be more or less agile, depending largely upon the quality of the aileron design, not something I've seen discussed. The aircraft are not optimised for the same conditions: which would be described as the better performer would depend upon where they were fighting and against whom.