I have used various trilams and both 7mm Atlan and O'Neil 7mm/5mm neoprene dry suits. Both were excellent suits.
I like the diagonal front zip from the standpoint of being easy to get into but despise the fit that results from the neccesarily longer torso needed to allow you to get your head in the diagonal opening. I have found that with a very slight amount of slack in the shoulders, it is possible for you to zip yourself into a back entry neoprene suit and it is easy to unzip yourself by clipping a 3' lanyard onto the zipper pull.
The zipper should be as heavy duty as practical. The zipper on my Diamond trilam was exceptional. Most others have been lighter and do not hold up as well.
From a commercial diving standpoint, I don't like cuff dumps as they always seem to get in the way. Same thing when diving with a deco bottle. And from a technical perspective, the cuff dump competes for forearm real estate where I would rather have a slate and bottom timer. I don't mind the sight roll needed to use a shoulder dump.
I am not a fan of the restiction added by attached hoods and prefer a neoprene seal and separate hood combination with an additional neck warmer if needed (it usually is not).
I like the low profile skin-in neoprene wrist seals on the O'Neil drysuits. However I do not like their use of 5mm neoprene on the sleeves. You lose a lot of warmth for relatively little gain in flexibility. It's what keeps it from being the perfect neoprene drysuit in my opinion.
Taping the inside of the neck seal joints is essential to prevent them from tearing.
Taping all inside seams should be considered mandatory.
Kneepads are a gotta have item on a neoprene suit, but they also need to have some stretch in them to prevent any restriction in mobility.
Thigh pockets are a plus for things like finger spools, dive knife, z-knife, etc.
A pee zip, or just enough extra room in that area to install a pee valve would also be desireable. For a neoprene suit, a hard rubber pad in the appropriate area where a pee valve could then be easily user installed would be a nice idea.
My preference in boots is a 7mm boot with a molded on sole. Care should be taken to avoid excess sole material on the sides as for a diver with wide feet, this will result in cramping.
A wide foot boot option would be greatly appreciated. As it is I have size 10 feet but have to go to size 12 boots to get enough width.
Light weight neoprene socks lack warmth and durability. Heavy rubber coatings just require excessive room in foot pockets. Hard sole "Rock Boots" are ok if you run around on rocks before or after dives, but involve to many comfort size and warmth restrictions to be desireable on 90% of recreational suits. Boat divers have zero need for them.
In my opinion, any drysuit design involves compromises and rather than developing a suit that does everything ok (and excels at nothing) it makes more sense to identify a specific market and design a suit for that market that meets those needs completely. So if you are designing a neoprene suit, target what neoprene does best.
In my opinion neoprene suits have three advantages.
1. Extreme warmth with lighter undergarments. I routinely take mine to 150 ft and while compression occurs, they are still warmer than a trilam and require less air and less management.
2. The potential to acheive a snug fit (with no loss of mobility due to the stretch of the material) translates into a much more streamlined drysuit (no folds or wrinkles on the surface) that has less air in it (without an uncomfortable squeeze) which all tend to make them swim much more like a wet suit with none of the positional limitations common to shell suit designs.
3. Low cost compared to trilams and vucanized rubber suits. I'd rather be able to spend $500 each for three neoprene suits over the years rather than spend $1500 on a trilam that has to last the same number of years.
Compressed neoprene suits were made popular by DUI (CF200, etc) but don't achieve number 1 to any great degree and fail to acheive 2 and 3 to any degee at all.
Field testing of the design is critical. It needs to be in cold water (50 degrees to 32 degrees) by real divers and at depths below 100'. When you get to that point, send me one, I'd be happy to test it.
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