"He was walking in half stride."

"He was walking at half stride."

"He stopped in half stride."

"He stopped at half stride."

Are those phrases involving "stride" grammatical? I intend the first pair to mean that he was walking at half speed, and the second pair to mean that he stop abruptly, as if one foot was still in midair.
They're not what would usually be said (whether they're technically correct or not). "Stride" here is very awkward. In the first pair you should say something like "He was walking slowly" (because what does "at half speed" mean in this context? If it means "half of his usual pace" then say that). In the second pair you should say "He stopped [in] midstep."
Then, "at/in half stride" could still be grammtical?
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They may not be strictly grammatically correct, but similar usage is quite common. Is there some bet at stake?
Therefore, "in/at half stride" is not standard English?
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