The trip was sweet. It was extremely easy to travel with the shredder, but some of the other gear got heavy as we traveled around. But we made it around the country traveling by bus with minimal problems (a couple of timing issues but that was it). I made a bag for the boat and the airline checked it without any issues. Once we were down there I attached the boat to a external frame (cut off the pack) with cam straps. It was a pretty smooth way to carry it even while we were walking around Turri in the rain trying to find the hotel.
If you are a boater, I am guessing you are if you are buying a shredder, then I would suggest trying to either bring down the shredder or trying to get a kayak. I dont know to me riding custy is just not the same as boating by yourself. We hoped on and paddled along with a bunch of commercial trips and that was really easy. Most companies will charge like $20ish a person for a ride to the river and lunch. Then you can get paddles from them and dont have to worry about setting up shuttles with drivers.
We spent most of our river time on the Pacuare...it was just difficult to run other water when you have a run that beautiful right there. We were going to go up North to Arenal but with the whole eathquake we decided to avoid it. I hear that the Rio Toro is a great river to run up there (but I have heard mixed information about the water quality). The word on the street is the Rio Sarapique is no more because of land slides that hit the river and the dam breaking (but who knows by the time you get down there it could be a sweet new river...1st decents?)
The shredder is a great boat for down there...easy to put where you want and fits in a lot of small slots. The river that runs down the Osa is supposed to be beautiful (just like the rest of the country) and could be a possible multi-day.
When you go down there I would definatly talk to Matt J and Kristen. They are great people who will do whatever they can to help you out. They run mostly on the Rio Pacuare but might be interested in doing a different trip. If nothing else they can point you in the right direction. Also check out costaricacreeking.com It is a great site that is not being used very much but has potential for a lot of beta.
Let me know when you start planning the trip further if you have any questions. I would be glad to help you out however I can...we got lots of help from many different people along the way and I would be stoked to return the favor however I could.
Also if you dont already have it Chasing Jaguars, (amazon.com) is a great guide book for all of CR. little outdated but still a lot of valuable info.