Size 4 - chest = 37.75"
Size 6 - chest = 38.75"
Size 6 - I think 6 is the right size even if it is a pulling a little at my stomach. An 8P might be the best fit. The sleeves would be a better length. However, I do tend to prefer regular sized tops over petite. I have seen all three choices and like them all. I can't remember if the white is sheer or not. The silk fabric isn't ultra thin, but it's not thick either. Check it out - on The Stylized Life.
A closer view. The sleeve length is not too bad on this regular size. I probably would feel more comfortable in the regular over petite. I would try a regular 8 to see about getting a slouchy feel and eliminate the issue of creating a wonky white line going down the front as it grabs my stomach.Yes, we tore that fitting room up, but we do pick up everything before we leave.
One of the issues I'm having w/tipped tops in general is that they're so pajama-y and end up looking like pjs or scrubs on me. You would think that the tipped design would be enough, but I would have to add some style to my ensemble and not view it as a throw-on top. Which kind of defeats the purpose of the style, if you ask me. I'd probably wear a white tank under or even navy, open up that third button and finish with long layering necklaces.