OK - so my tall and skinny 3-year-old measures 19" around the chest and tummy (6-12 mo size!), but is 39" tall (so I'll have to add a little length to the 3T to get it where I want it). I just drafted the front and back panels of the dress in the 12-18 mo with 3T length. I kept the armscyes the 3T length because it made sense to me, but I only drew them to the 12-18 mo width, and then the body/skirt is also 12-18 mo width. I hope this makes sense. Anyway, I am not sure this is the correct approach. I'm making a "wearable muslin" of this dress in corduroy before tackling the lilac velveteen I bought for DD1's Christmas dress, but if my approach is wrong, I'd love to redraft before even starting the "muslin."
Also, if my approach is correct, what do I do with the sleeves? I don't want them to be overly poufy - I love this dress when it is fitted properly but some versions I have seen are a little too voluminous for my taste. It doesn't quite make sense to me that I would use the straight 3T sleeve - it seems I'd need to narrow it but keep it the 3T length. Any input?