Ellaroo is nice and thin. I liked my Wrapsody Bali Breeze and my stretch hybrid up to about 25 lbs and then they started getting a little diggy-any of those can be used with a back carry though. If it's hot enough a wrap will probably just be really uncomfortable. You may consider a meshy/solar veil ring sling or even a wrap convert ring sling if you want to go with the longest possible usage. I also really like my Bara Barn which I haven't had through a summer yet but it's really lightweight and I can do a no sew ring sling, rebozo, or any size 2 carry with. They're kinda hard to find in the US at least but I plan to use it as my go to for a ruck tied under the bum this summer with my toddler when I'm not using my Kinderpack with Kool knit
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