Hee hee - I'm here Nelle!!!

Anna, what kind of ring sling do you have? It could be that the shoulder style is not suited to your body or that it's not adjusted the best way (or that the body is not wide enough) - bubs should still be able to sit comfortably in the hip position at an age much older than three months. So it might be worth persevering with. There are heaps of great videos on Youtube that show the best adjustment. That said, some ring slings are more supportive for larger babies than others, and most people find two shouldered carriers more comfortable for long carries. From what you have said that you want from a carrier, you might be best off with both a ring sling or pouch and a two shouldered carrier like a mei tai or SSC (soft structured carrier), as no one carrier will meet all of your needs exactly.

Any carrier is going to be hot up here in summer. So I wouldn't recommend buying a carrier simply because it uses a cooler material, most meshes for example are not very supportive. I had a baby rock carrier and these are designed for hot climates, but I personally found it quite unsupportive.

Currently I have a Connecta (which is a mei tai style SSC) made from solarweave. This is a lightweight fabric that provides 90% UV protection and is very quick to dry - perfect for up here if you get caught in the rain (or want to wear your carrier in the pool/shower). I would recommend it highly. They are only available by order from the UK.

An SSC is preferable to a mei tai if you don't want straps dragging in the wet ground, although if you are thinking of a mei tai I would second Nelle's recommendation that a babyhawk is prettier. ( Nelle). They have a better headrest to a catbirdbaby too. Catbirdbabies have a narrower strap angle (good for narrow shoulders) and are a little cooler than a BH, but TBH I think that the difference is going to be negligible in this climate.

HTH!!