Maximum concealment is achieved when corset fits snugly on your body. Compression from the garment pulls the gun in closer, while the holster itself is specially lined to smooth the rigid edges of your gun and mask its outline. Your corset should feel snug rather than too big - this helps with concealment too. So if you are between sizes, go smaller.
Measure at the smallest part of your natural waist. Please order based on the size chart and not on any past corsets you may have purchased - product fabrics have changed over time.
If you are exactly between sizes, go a size smaller.
If there's a big difference between your waist and hips, cinch the top on the tightest hook and eye row and the bottom on a looser hook and eye row.
If you are short-waisted, leave the top two hooks unfastened and tuck the corners under. This works best for smaller guns.