No matter what the situation is, as long as it's within 800 meters, Huan Yu would be in control. Even a B-Class Time Traveler would necessarily die.
Moreover, it's not certain that the opponent can control a B-Class Expert.
Qing Chen calculated, previously estimating that he could master an effective range of 2600 meters in 7 days, but he overestimated himself and underestimated the difficulty.
As it looks now, it would take at least 12 days, and that's just accounting for wind speed.
Once he graduates completely from the wind speed training, he needs to add training at different altitudes.
This is a long-term training plan.
Accumulate steadily to achieve a sudden breakthrough.