In RP, the distinction between ‘penis’ /ˈpiːnɪs/ and ‘peonies’ /ˈpiːənɪz/ is very clear.
However, in Scottish English, the /ə/ in the latter word is omitted, so in my current mixture of RP and Scottish English the two words become almost homophonous: /ˈpiːnɪs/ vs. /ˈpiːnɪz/.
However, applying the standard rules of Scottish English (not of Scots!) would make the difference somewhat clearer – you would expect the difference to be /’pinɪs/ [ˈpinɪs] vs. /ˈpine#z/ [ˈpineːz].
The difference is even bigger, though.
Something happens to the first vowel in peonies, so the difference is actually [ˈpinɪs] vs. [ˈpiːneːz], as if it were /ˈpi#ne#z/ (almost like a hypothetical compound *pea-nays).
I wonder what’s going on – in Scottish English vowel length is normally predictable if you know the morphology of the word.