sense-cents, tense-tents, mince-mints, prince-prints etc.

D, Do you pronounce ''once'' and ''wants'' the same way?

I don't "wants" = /wonts/ & "once" = /w^ns/.

I have heard that 't' (the one that crops up in 'fence') called 'sycophantic t'.
I can't produce 'fence', 'prince', etc. without sycophantic t.
However, I'm not so sure about the voiced counterpart, sycophantic d.
I think I may hear a difference between "Ben's" and "bends". (We all deceive ourselves a great deal in these matters, so it's possible I am saying "Len's" and "lends" the same and just imagining a difference. Don't know!) Maybe I drop the 'd' in "bends" rather than adding the 'd' to "Ben's".

Besides the t and d pair after n, the p and b pair after m, and the k and g pair after ng all exhibit parallel behavior.

Does "glimpse" really need the 'p' or would it occur "sycophantically" anyway in "glimse"? Same for "exempt", "redemption". "Warmth" doesn't need the 'p', even though it's there (microscopically, let's say). Did the "b" in "lamb" (and similar words) get there because of a sycophantic "b" that popped up in "lams"? Can you hear the 'k' in 'length'? (Some people say 'lenth'; I'm not talking about that pronunciation.) Does the plural of "song" add only the 'z' sound to the singular? Or does it add both sycophantic 'g' and 'z'?

>>I think I may hear a difference between "Ben's" and "bends". (We all deceive ourselves a great deal in these matters, so it's possible I am saying "Len's" and "lends" the same and just imagining a difference. Don't know!) Maybe I drop the 'd' in "bends" rather than adding the 'd' to "Ben's"<<

I'm sure of it (the deception). If you used an oscilloscope to analyse your pronunciation of these word pairs, I'm positive they'd come out similarly, if not, the same. Each word in a pair (eg. lens, lends) might display a little differently from the other, but each with some amount of intruding 'd', 't', etc as appropriate. I couldn't imagine it otherwise.