Everyone is thinking this.... but not saying it... BAD IDEA.
Might as well save weight and not take PFDs as well. If you have any sealing failure, or don't screw the hatch. Or the more probable...Start using those compartments for storage.
$60 and 20 pounds... and it is there.
I can't see how he can use the compartments given the below part (b). I also see that he is not listening to anyone, so more power to him.
Basic Flotation Material Requirements
FEDERAL LAW: 183.112 Flotation material and air chambers.
(a) Flotation materials must meet the requirements in Sec. 183.114 as listed in Table 183.114 when used in the: (1) Engine room bilge, (2) engine room, or (3) bilge, unless located in a sealed compartment.
(b) Air chambers used to meet the flotation requirements of this subpart must not be integral with the hull.