Besides looking pretty cool IMHO, the general idea is to lessen the effect of boarding following seas...sort of 'cross your heart' engineering, lift and separate.
As ughmo points out, the loss of some storage is a trade-off as is the added complication of mounting a wind vane and other 'cruising hardware' due to the compound curves as oppose to a relatively flat transom.
BTW, I saw the pics and artist renderings of your boat...interesting profile. Got any pics of your boat you can share? Bet she's a 'true tracker' in a seaway with the fullkeel and the rudder that far aft. Nice looking boat and congrats on your stewardship.
i have some prints from the old owner, i will try and get scaned soon and upload.
I was thinking that it would be for the following seas, and when the boat is really leaned, it gives a better exit line for the water..
the other think i noticed is that when we apply helm, the rudder does not simply trun side to side, is swings up and sidewards.
I have quickly come to realie that there are a lot of tradeoffs for mounting items on the rear, and some soorage issues as well, just wanted to know what the trade off was.