Hi Kent.
Generally it's not too bad: if you are crossing the border one way or another, you have to file an ICAO flight plan.
You also have to send a copy to customs 3 hrs before each border crossing.
This is easiest done by filing the flightplan from the net and also write in the remarks section that you want a copy of the flight plan to be sent to customs.
I like to file both flightplans at the same time, so I don't have to worry about filing the return leg when landing in remote places.
If you then schould need to change your dep time for example, it's just a quick phone call.
You also have to takeoff and land at customs approved fields, but in fact most of the remote fields are approved, and ofcourse all fields with scheduled traffic.
And there's ALOT (hundreds) of nice airstrips available within Scandinavia when you're flying a RV!
For most airstrips and airports, you have to get a PPR but that's also just a quick phone-call.
You don't need a passport within Scandinavia, but it's a good idea to bring it anyway since it can be used as an ID, for example when using a CC.
When I pick airports or airstrips to go to, I pick the ones without scheduled airtraffic if I can, because those doesn't have security personell. You just land somewhere on the grass, park your plane and walk away. That's the way it schould be when you're RV-ing around...
The above notes is for Norway, Sweden and Denmark. It might be alittle different in other countries in Europe, but not much.
Just for fun: here's a link to our Norwegain planning site:
www.ippc.no
The upper left corner ("ippc menu") is a nice place to start.
In addition, some countries have restrictions for foreign experimentals, but many of the countries have a mutual agreement.