i was makng these type of things twenty years ago every now and again someone still wants one i got heavily ridiculed for them still got some down the back shed ill post some,they actully worked alright you can feel something nice one guy that i do boards for still swears by them i remember showing glen winton and he loved em i think he came second in a world title on one cant remember wild times they were anyway there is somethig there.
the point of the narrow hips on snowboards or skis works only on icey slopes and they are made for a smaller turn radius.
The new parabolic skis/snowboard came when the carving turns were discovered. So if ur board has the enough felx the parabolic thing will make his job and ur turns will have less radius.