I'm new to message boards so bear with me, although I've watched this one without posting for a couple years.
First off, we are not here 'just to be different.' Our harnesses and flat backplates are the sum of more than a year of trial, design, and development of an idea. Prior to that, several years of diving and comparing every setup known to man, among a group of very fine recreational, cave, wreck, and deep divers and teachers from several different disciplines. (This resulted in many 'lively' discussions...

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The flat backplate is for single tank diving only, it will NOT work, nor is it designed for rigging doubles. We will be introducing a doubles plate very soon, which will be similar to the myriad of others out there, except that ours is constructed with 316 L SS, and will cost significantly less.
Our flat backplate was designed with the idea of getting rid of the single tank adaptor. In OUR HUMBLE OPINION, we felt that there had to be a better way of utilizing the many benefits of a Backplate and Harness, without having to modify a doubles backplate with a single tank adaptor.
So far, comfort with the plate has been excellent, but we're always open to new ideas. We are thinking of introducing a contoured pad for 'bony spines' but haven't seen a want for it yet. Any opinions?
As far as the chest strap, and again our very humble opinion, We feel that most people (but certainly not all) will achieve a better fit, and support / distribution with less underarm chafe using shoulder straps which come straight across the shoulder, and a sternum strap mounted on our 4 point harness rings across the chest. We will gladly manufacture a harness without these features as well.
The crotch strap -
It is our error to have not put up more pictures of our gear, and we're working on that right now. The harness pictured represents one possible combination out of many.
JET Harness custom builds each harness for its wearer. If you'd like a crotch strap, just let us know, and we'll put one on. 1 inch, 2 inch, soft, hard, you name it. We'll build cross the back, cross your heart, straight, padded, no pads, rings, kitchen sink, plain, etc. Personally, I must have a crotch strap for double tank dives, but when diving with a single, I don't like it.
Our mantra is that there are many different philosophies for setups out there, and we are very excited about serving people exactly what they want. Building our harnesses one at a time for the individual is how we will accomplish this.
If you're partial to a DIR setup, (correct me if I'm wrong) but I think the best way, since it is one piece of continuous webbing is to simply buy the raw material and build it yourself, it's easy!
Thanks for reading!