I understood that it's only really a problem if flying above the 500mb pressure level (roughly FL180). It depends very much on how deep you're going to be. Amazingly, a depth of 10 metres (30') means you have the 'weight' of 2 atmospheres on top of you instead of just the one; and 20m is 3 atmospheres etc...
Maybe a posting in the medical forum would be a good idea or better still a chat with an AME.
I believe you're correct about the 24hr rule but personally I'm scared witless by the whole DCS scenario and will stick to paddling....forever!
