[dsraven]

I'm with the penetrating oil group. I had a boat with teak finishes and thats what worked best. it was under a canvas boat cover when not in use but still needed to be oiled fairly often. it lived outside year round.
with that in mind I used a steel bed in my old project. i would consider a composite decking bed otherwise. since you have the wood already I would say use an oil that has good UV protection and, after you have fit the pieces in mock up, take it all apart again, apply several coats on all sides until it won't absorb anymore, come back in a few days and do it all over again until it won't absorb anymore. then let it sit overnight, wipe it down and install it. keep the oil handy for future applications.