I can provide a few general comments. A custom suit is often the best option for people who fall outside of typical size recommendations.
On the other hand, a lot depends on the type of suit and the temperature. If the water is cold, maybe 60 or less, then it is really essential that the wetsuit fits well. If a diver is going to warm locations, where the water temperature is above 75 or 80, there is a lot more flexibility with regard to wetsuit sizing.
In general, with regard to our wetsuits, we recommend that if someone is a little outside of the sizing guidelines, then it is more important to match the weight rather than the height.
This works best for people who are "a little short for their weight" because if a sleeve or a pant cuff is a little long, they can often be rolled up. Someone who is tall and skinny, might be fine with a little skin showing at the sleeve and ankle if the water is 75- 80 degrees and they are wearing a thin, full suit. If a thin person is diving in 50 degree water and wearing a 7 mm suit, short sleeves might be unacceptable - almost as bad as a loose suit which allows water to slosh around inside the suit.
People who fall within our sizing guidelines should find their suit fits VERY well, however some people who do not want to pay the considerable premium (and sometimes wait) for a custom suit, may be very comfortable and satisfied with a suit that has a wrinkle here and there. Modern, high quality wetsuits have a good bit of elasticity and can accommodate a wide variety of body shapes.
Also, in general, thinner suits are more forgiving (more elastic) than a thicker suit, which may provide a little more leeway when considering if an off the shelf suit will provide an acceptable fit.
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