Ken.
I don't think you will find may old timers left who flew on Heavy's during WW2, but for what it's worth, I spent 5 years as a Wireless Op with the RAF in the 50's. The T1154 was well on its way out at that time, and although it had done it's job to perfection throughout the war, there is no escaping the fact that it is possibly one of the crudest designed transmitters ever built.
The relevant AP reference to the 'Magnetic Relay type 85' specified that it is designed to operate at speeds of 25 WPM or more. Given the distance the contacts must travel and return each time the key is depressed, and the simple mechanical design of the assembly, this estimate seems absurd to say the least. A good wireless operator could send at 25WPM using an RAF type 'D' ground station key, but not on an aircraft Bathtub key while wearing leather gauntlets.
After a great deal of careful contact adjustment on my own treasured T1154, the best it can do is 15 - 18 WPM, with a regulated 6.5 Volt supply for the keying voltage. The relay undergoes a full movement each time the key is closed, so the problem of clipping a dot or dash would not be confined to the first character sent, but would continue throughout the transmission.