Hey! This is my first time ordering a onesie online and I'm not sure which size is right for me. Can anyone who's ordered from babykins before share some advice?

Here's a ink to the specific product and sizing chart: Original Adult Onezie T-Shirt - Babykins & Kins Products

I'm 6'.1'', but I have a fairly narrow chest which I measured at about 40''. Did you guys find that the chest size really mattered? I'm worried that it's going to be too baggy if I order the S-Large.

Any help is appreciated. Thanks!