i guess the rigid bulkhd comparison come off best in that something has to be added to other yaks in order for them to float(or barely float). so the comparmentalization of 3 chambers (front, back, and you)gives a whole bunch of safety in a system thats been used for a while now(ships,subs etc). and thats more im portant than any single hole you'll get.

so the (rigid)bulkhead system is a good idea in that automatically some redundant and large floatation.

but if you're going to do it use some of the other suggestions here to minimize the stress riser possibility and as well airbags are just as easily added they give a whole other order of redundancy and safety and utility for jamming in the gear so it doesnt move - like itll keep the gear low so the yak sorta acts selfrighting if upside down or rolling.

another idea for putting in non stress fillets may be to cut a wedge of foam the inside perimeter of the yak and glue(temporary or tape or jam in) in place, make a wd bulkhead 1in less in radius than the yak all around, lay glass 3in larger that radius on inside, thumbtack perimeter to keep in place, flip, layglass same 3in larger, thumtack, then fold the extra4in back and thumtack and jam the b/h on the foam, release the last thumtacks and spread the excess over the foam to the yak, set up and pull the foam and other tacks if possible. maybe some 20# test was wrapped around ea tack first to just pull out.

i'd test fit first and sand the excess foam wedge to a curve.

might be simple and quick , might be a mess. so mask first!

-mick