I've been intrigued by Gwiz's post
that he likes to sit up out of the seat, on a pool noodle in front of the rear crossbar. I've tried it (without the noodle) and it really is a great place to sit. You can turn around and you can lean out over the aka. I enjoy it more than hiking out on the tramps. I was also out with a friend recently, with me kneeling in the rear cargo well. The boat sat low in the water and was clearly slower, until we found ourselves running before a stiff breeze, with lots of wind waves - normally bow-burying territory. The boat performed better than I have ever known it to in those conditions, because the bow was pointing so high. It got me wondering if shifting one's weight to the back mightn't be a good tactic. I found that sitting directly on the crossbar is fun, but you quickly get a numb bum. I've rigged up a platform with PVC pipe and it is fairly comfortable.
Then I tried fitting my trusty Ocean Kayak seat and it was even better.
Needless to say, you can't pedal from that position, but I have no trouble steering with my makeshift tiller extension. I haven't yet encountered any windy, wavy conditions to see how effective shifting my weight that far back is, but for general sailing, it is a buzz. I may extend the platform so I can sit even further back.