The longest flight until now was 632 m
Covering 632 m in Flight #9 was possible due to the fact that the helicopter was 'sliding down' from - 2569 at departure to -2579 at arrival.
On contrary, flight #21 M->N shall be climbing out of the -2570 'pit' up to... say, -2565 (=+5m), so I'm not sure that 'ordinary' ~400 m for 170 sec may be covered.
Next limitation is 1000 m for communications. Helicopter may wait for a long time at 'Field N', until Perseverance reappears at the northern side of Seitah region in a direct LOS view at a distance <1000 m.
-Cherurbino