Ordered one of the Saddlemen adventure seats from crusiercustomizing.com.
The seat is relatively new and not too expensive ($360 delivered) so I want to try it before shipping off a spare seat to Russell Day Long for a long distance seat. The issue with Russell is the seats really work (1500 mile day with no butt complaints) however it would probably be pretty ugly on a F800GS.
Saddlemen does not require your seat pan, so you have two seats.
Here's a forum thread about it.
Here's a link
to the adventure seat line at Saddlemen.
Will post a ride report once I get it.