I get overheated pretty easily and was thinking this would be a good option for babywearing- especially this summer. Also, they are just so pretty!
Also, what size should I get? I am planning on doing weight watchers soon, but am currently about a size 18.
Just make sure you get the thinner ones if your intent is to have it for hot weather... there is more than one thickness for Vatanai's, though majority are thinner, by my understanding (the thicker ones that came out earlier this year were pretty popular and sold out quickly per the person I talked to at Granola Babies).
I went in to Granola Babies last weekend (she's one of the few US distributors..I'm so lucky to live in SoCal and be able to look at them in person) to look at the labrynths she had in stock. I tried out a hypothetical FWCC with a baby-size insert and I was OK w/a 4.5, with enough end to tie off no problem. I was about a 16 pre-pregn'y. Hope that gives you an idea of whether a 4.5 could work for you. If you're planning a wrap style that requires more length than a FWCC, then you might consider the 5 though.
FWIW, in person I liked the material and how close it was to being broken in right out of the box (though I'm sure some washes won't hurt), compared to some of the other brands she carried. Since hubby spent a similar amount on the Beco Gemini carrier, I didn't feel bad spending the amount I did on the Vat.