To my great astonishment I did find out that at the both ends of the pin of
the ss fin strap clip manta is actually selling there are merely two buttons
which are pressed on the pin as depicted in the picture at
http://users.pandora.be/safe-diving/d_fout1.htm (text in dutch, sorry).
I believe this to be a serious risk as these might come loose one way or
another and hence the diver might lose his fins, losing the ability to
propell him or herself thru the water. In extreme harsh diving conditions
this could be a disaster.
I have emailed manta for a reaction. I will have to keep trying as I am
getting "over quota" on, their address ...
Dive safe
Xavier