Wendy once bubbled...
Are you putting them on yur primary and backup regs? The reason I ask is that I dive with a buddy that has a secure and I can't breathe from her reg with teh secure on it when we do OOA drills. Her jaw is longer than mine and her mouth piece won't fit my mouth, its a terrible experience for me ...snip
Wendy,
The length thing is easy to solve. Lots of people get a gag reflex from the standard Secure mouthpiece.
Simply trim the rear portion of the mouthpiece off until it does not bother you or your buddy. I always had to trim my sports mouthpieces too .... not good to be barfing in the huddle at the 50 yard line. I have mine trimmed so they only go to about the second molar and they still work fine for me and anyone i have buddied up with so far.
I've found that most peoples teeth and mouths are close enough so if trimmed properly, the Secures seal up nicely. Like Rich said, a little bit of trimming works for most.