So, I have a general pronunciation quandary… I recently signed on for the northern course because I tend to like its vocabulary better (based on what I’ve seen of Gogledd / De variations in Duolingo, anyway). However, I’m having a rather difficult time pronouncing ‘u’ correctly for that accent. I can hear the difference from ‘i’ quite clearly, and I come close to getting it right on some words (e.g. when it’s at the end of a word, like dysgu, Cymru, etc.), but it usually wants to come out sounding like ‘i’ when I’m not making a conscious effort and speaking slowly. Will it end up sounding blatantly odd if I’m using the northern vocabulary with a more southern vowel pronunciation? Should I switch to the southern course since I’m so early in the process? Or, should I just keep going and hope my tongue learns to adapt? (Am I overthinking this to a ridiculous degree? 
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Yes, I’m afraid so!
Don’t worry - some areas even in the North don’t do the full on u, and those that do will just know that you’re from elsewhere if your 'u’s sound more like 'i’s. It’s not a huge problem.
Trust me - I’ve been using Northern vocab with a Hwntw accent in Caernarfon for nigh on 20 years! 
Thanks for the reassurance! It really was getting to be a distraction during the challenges. My brain would get so sidetracked focusing on the pronunciation that’d I’d sometimes miss the next sentence. I had a feeling it was just the perfectionist side of me kicking in again, but that side often needs to hear from an outside person in order to quiet down. In all honesty, I should be thrilled if I can eventually tone down my American accent enough to sound like I’m simply from a different part of Wales. 
I’ve never figured out how to make that sound, but it really doesn’t matter. My partner (who’s a native Welsh speaker) tells me that many people who learn (northern) Welsh as a second language struggle with the u sound. But luckily for us learners it’s not necessary at all! It’s basically a regional accent thing. You don’t need to mimic a Gwynedd accent to speak Welsh intelligibly!
Thanks, Alan. It’s good to know I’m not alone in struggling with that sound – and that it’s not critical for me to get it. 
I’ll keep trying for the sake of it, but won’t worry about it or let it slow me down.
To make that sound you need to lower a bit the back part of your tongue when you say ‘i’. In other words, to open your throat a little wider, than for ‘i’. 
Oh, good to hear – that’s what I was attempting to do, because the resulting sound was at least close to what I heard. I wasn’t sure if that was actually how it’s done, though. Thanks for the tip!
I’m very happy that it helped. And if you lower your tongue/ open your throat even more, you’ll get a clear ‘y’ sound (‘y’ as ‘the’ or ‘y’ in ‘dy frawd’ and so on). But don’t overdo it, if you open your throat like Luciano Pavarotti, instead of Welsh sound, you’ll get the perfect Estonian ‘õ’. 
Ooo, now I’m going to have to look up some audio for that Estonian o!
Well, if you are not afraid of words like ‘voiceless palatal fricative’ https://en.wikipedia.org/wiki/Welsh_phonology can be really useful.
So. This one is Welsh https://en.wikipedia.org/wiki/Close_central_unrounded_vowel (and also Russian by the way)
This one is Estonian https://en.wikipedia.org/wiki/Close_back_unrounded_vowel
Fantastic, thanks! I’m no linguist, but I love reading that sort of in-depth information.
It is much like the ‘u’ in ‘la plume de ma tante.’.
I don’t think it is. That would be close to the German ü and that’s definitely not correct.
I defer to your expertise, but that is how we used it when I was at school in Colwyn Bay 1939-42.
Accents change over the years and there are regional variations. I remember, at a meeting of Cymdeithas Hynafiaethau Cymru, learned professors having sharp intakes of breath at the accent of an Abergele colleague, so I sidled up and said ‘it’s the local lingo; we all do it here…’