I've mounted my Gorillapod a little differently, mainly to get a lower point of view for the housing. Plus the L&M tripod mount would have ended up at over $200 shipped to here.
Following Dan's advice I ordered 6 extra links but didn't just use them for extending each leg. I disconnected one of the legs and added all of the extra links to it and stuck 4 or 5 links of it up the rear of the housing, between the 2 pods. The size is perfect. It's very tight. When stored up it needs to curve out a bit like a scorpion's tail so that it doesn't obscure the line of sight for the IR signal from the back door of the housing to the battery pods. I've cut the rubber off 2 of the links so it doesn't interfere with the door.
I hacksawed the top of the gorillapod in 2 and mounted one half on each side of a new battery pod guard that I've made (details of my older battery pod guard, made from the bottom of a plastic bin, are
here). So far I've just used a single stainless steel self-tapping screw from the rear, into the "top" of the mount. To be honest it would be better to get an extra top piece from Joby so it doesn't need to be cut in half. That would be stronger.
On the surface the legs can't hold the housing up, but underwater they can. It's all a bit wobbly but once it's settled it's possible to hold a shot nice and still. Sometimes I used it flat on the seabed so the legs stick straight out like stabilizers, and then hold the ends of the legs rather than the housing.
I'm actually wondering about roughing up the links a bit so that they're a tighter fit and less flexible. I guess they might get tighter as they age.
Really I need to get a stronger guard/mount fabricated out of sheet aluminium because the plastic bin is too flexible. If I draw it up, does anyone know a place that can weld something like that up in aluminium sheet/plate?