The adhesive mount is definitely not sufficient to use alone on a bodyboard!
You can use the surf expansion kit. You'll need to customize it a bit like you see in Chuck's vids (see additional illustration below) and mount it with two leash plugs, but be careful, this is only a suggestion and this method is not endorsed by GoPro, so its technically at your own risk. No matter what, I always rig a 2nd tether to whatever I am mounting it to, just in case the main mount snaps or is lost somehow, but so far so good.
You might also consider a helmet mount. We stock both at AtlanticBodyboards.com and if you mention swellinfo.com we'll give you a 10% discount off MSRP.