Hi Wookie, how's things?
I'm at the early stages of planning a trip for this summer. Thinking about a similar route, although I might take the ferry Travemunde - Helsinki to cut down on the miles. The X-challenge has a big tank and re-upholstered seat now, but no point in wearing myself out on the autobahn.
The initial idea is for around 2 weeks, hopefully with some off-road riding somewhere on the journey, on a low budget so wild camping may well be included. Any advice/poi etc gratefully accepted.