The speed of the four heavy cruisers definitely exceeded 33 knots, and even if they didn't reach 34.5 knots, they were close to 34 knots.
Moreover, neither the "Imperial Capital" nor the "Peijing" was able to achieve a speed of 31 knots, only maintaining around 30 knots.
To figure out exactly how fast they could go, Li Mingbo had even made a special trip to the engine room to consult with several experienced officers. They could reach 31 knots if they only needed to sail for a few hours, consequences be damned, but to sustain a higher speed for a longer duration, they had to keep their speed under 30 knots, and not exceed that by much, otherwise the power system could fail at any moment.
Not to mention anything else, just one boiler explosion and it would be all over.
Now, not just Li Mingbo, but Bai Zhizhan was also anxious.