I hope this is ok to post here and proves to be of interest. I have just been looking at differences in syllable stress (by English speakers), and have come across this paper. It compares stresses in English, Welsh English and Welsh. It also mentions the lengthening of the vowel in the syllable preceding the stressed vowel - something that I find that I am doing, even though I’m not originally from Wales - https://www.internationalphoneticassociation.org/icphs-proceedings/ICPhS2011/OnlineProceedings/RegularSession/Webb/Webb.pdf
Sorry, that should be the consonant immediately following the stressed syllable (I think).
Thanks for sharing this John. The lengthening of post-stress consonants (particularly “d”) is something I often notice, and is one of the things I love hearing in spoken Welsh. I could not find a mention of the size of the two word lists referred to in the article, and the sample table only lists 4 “n” and “s” words. I don’t know enough about statistics in linguistics to judge if the small sizes of the two test groups (5 and 6), in combination with a possibly small word sample size makes some of the conclusions statistically valid or not, but it seems intuitively correct to me.