Good RFP response writing reflects the client’s language. Here’s one example of how that works. Or doesn’t work, sometimes.
Whilst rummaging amongst proposal sections, I didst see usages considered archaic in the New World, forsooth.
Well, OK, I didn’t see “didst” or “forsooth” but I did see “whilst” and “amongst.” And not for the first time, either.
Unless thou art writing for a British customer, knocketh it off and useth them not.