I am installing them in my ES. They are a fair amount of work to install and provide less benefit than maximum floatation. And, even with secondary hatches, your primary hatches should be made and maintained leak proof.

I'd be interested in other people's thoughts on this because I am still very much a novice kayaker. But, after reading "Deep Trouble", I try to be very cautious.

(Somewhat OT: What is the difference between paranoia and normal healthy fear?)