Well, as an update: I bought a Sprint July 2009. yay

Still looking at buying the Corbin seat. Got a quote from
www.vpw.com.au for $1015. Corbin only supply to USA customers and quote from UK for seat is $AU1139 and that is without delivery.
yep, already had seat re-shaped before we rode to Adelaide. Had the front of the seat shaped upwards, etc, etc as mentioned by Ian.
The real problem is the seat mounting setup. The bolts being placed under the seat means the foam is very thin to allow bending it out of the road to get at the bolts. This thin foam does nothing for passenger comfort. I'm not sure how far you are riding with a pillion but Anna gets VERY uncomfortable after a couple of hours.
We bought an inflatable camp pillow after one day on the trip to Adelaide. This helped but was fairly bulky and raised her quite high up and wasn't really a solution.
I also manufactured some new foot pegs for Anna with some brackets and foot-boards from a Harley shop. I am still looking at the German foot-pegs and will purchase the 5cm drop-pegs and mount some floor-boards up to those.
At the end of the day I will always struggle to make the Sprint comfortable for all-day pillion touring because of the design of the bike (seat angle, seat mounting design, knee angle for Anna, etc).
My real problem is that she was very comfortable on the 109 and has known comfortableness on a bike. She has mentioned buying another 109 as a second bike.

So if finances ever allow I will be purchasing a cruiser for touring with Anna. And would be sorely tempted to trade the Sprint for a Daytona or a Speed Triple...