I've had this sentence to proofread a couple of times, so evidently the writer thinks my improvement is unnecessary:
It is possible to adjust the gas flow fast and accurately.
It's a formal, scientific context. I suggested changing it to:
It is possible to adjust the gas flow rapidly and accurately.
I realise that "fast" is also an adverb, but it strikes me as less suitable for a formal context and odd-sounding in combination with "and accurately", or maybe in that position in the sentence: it just sounds weird to me. Rather than just changing it again (and having the customer ignore it) I'd like to explain why I'm changing it, but all I can find online is people saying that "fast" is absolutely fine as an adverb (which is true in many contexts). What do others think?