I think you'll get a lot of interest in this. Where did you get the Neoprene? Can you buy a small piece? How Much $$ ? It would be interesting to post your longevity findings about it. I wonder how long it will last after stretching it over your head reguarly.

You said you researched it? Are some manufacturerers using this material now for diving drysuits?

It seems like latex seals are safe since the bulk of manufacturers use them and they seem to go after a few years and only when you pull it over your head. I never heard of one going after it's on. I once spoke to the rep from Kokatat about the use of silicone and the problem with it was that eventually it takes a set and will not stretch to the % needed to go over your head. Most paddlers complaints are about new seals being too tight. Most people get around 3 yrs out of latex ones - the neck seal being the most replaced.