Allan,

For the Wood Duck, just pushed into place. They just make sure that that massive cockpit area does not fill with water. Since the rear bulkhead and hatch form a watertight compartment, I'd say both bags in the front.

That being said, I've been using my WD12 since Okoumefest 2008 without float bags, sometimes in some pretty rough conditions. The spray skirt has been quite adequate for keeping the cockpit free of water. In good weather with no power boats around, I  go without the spray skirt. It takes some really rough water to fill that cockpit. I can even go completely over the side and get back in without filling the cockpit.

An alternative to float bags is a large dry bag, like the NRS Ricksak sold by CLC. The large one, for $27.00, will displace over 80 lbs of water. Just hold the mouth open and close the seal while the sack is empty and you have a jumbo float bag perfect for pushing up into the front of your Duck's cockpit. The sack also provides dry storage. As long as you only fill it half full, you still get plenty of buoyancy.

Have fun,

Laszlo

generally, as Laszlo mentioned, they aren't held in with anything, just jammed in place to fill up space.  I have tied my daughter's into her boat though.  I have homemade float backs shaped vaguely like her boat and on one I have a little tab I use for holding it in place with.  She has never been on any kind of open water, just a local lake, but it makes me feel better knowing it won't leave the boat.  Keeping it filled with air, on the other hand, has been a bit trickier.  I installed a camelback bite valve to allow her to blow it up occasionally to fix the issue of deflation.

FrankP