My 2 cents on the M4, I tried it for the first time this year we got over 20 fruit from 3 grafts I did 3 years ago. I was excited for coconut flavor but the only coconut I got from the M4 was aroma - there's definitely a strong hit of coconut in the aroma (once you cut it open - before that no smell at all which is really weird if the only mango you know is Haden which has a powerful, heavenly scent when ripe). But in the flavor I got citrus notes, maybe some piña colada especially near the shoulders. The flesh is sweetest at the shoulders and by the skin. Delicious mango.
I would definitely agree that it's sweetest by the skin. My wife picked up on some citrus when it was maybe a day under ripe for my preferences, which I didn't really appreciate and would verbalize it as "subacid". We all taste things differently. I will say to get the maximum coconut flavor I really let mine ripen to the point I see skin wrinkling at the top and even some on the bottom. At that point I almost always have been smelling coconut for about 3 days at the stem. That's how I like it best, and I do scrape along the skin as I eat. To each their own though. Don't know exactly where you are, but you're somewhere super tropical and at elevation so it's cool to see it's producing well in those circumstances too!