You can ignore that. File a flight plan and talk to ATC/FIS. Serbia has very limited RADAR coverage.
Some years ago, I had Montenegro chuck out a VFR flight plan which would have passed just offshore.
They wanted me to route via a specific IFR route. This is common in Greece, though it may have changed very recently with their airspace classification where they cannot insist on IFR routings (e.g. A14 from Corfu to Sitia) in Class G.
This is really rare as normally you can put anything on a VFR flight plan route and nobody will care much.
Down the Adriatic, there are various published VFR routes e.g. ADRIA1 here
but as you can see the 2013 Jepp charts don’t go very far to the south east.
I have never seen any evidence that anybody down there (Slovenia or Croatia, anyway) cares about these routes. Class G is Class G. They may have been originally published to assist very low level traffic flying down there at say 1000ft, especially of routing through bits of CAS, in being in a place on which they are more likely to get a transit. I always used to fly down there higher up – 8000ft or more.
Lovely, thanks! This trip seems more and more doable as I’m successfully clearing any doubts with your help here. Can’t wait to get going. 
An alternative way of interpreting the required routing is that they want the “Greek method” which is the IFR routes e.g.
You can see some waypoint names are shared with the VFR routes e.g. MOKUN.
To get these routes, buy the IFR enroute charts, or get a printout from somebody with an IFR flight planner like Jepp Flitestar.
To get these routes, buy the IFR enroute charts, or get a printout from somebody with an IFR flight planner like Jepp Flitestar.
… or just switch Skydemon in Airway Mode :)
I do this all the time, btw: When I fly VFR, I just file and fly IFR waypoints.
ATC knows what you’re talking about, and you can just stick the points in the FPL in your GPS…
These can be added in SkyDemon, too. 
You can ignore that. File a flight plan and talk to ATC/FIS. Serbia has very limited RADAR coverage.
I’m not sure about this. They expect you to report your position correctly. If flying VFR from Croatia to Serbia you’re expected to cross border at PEROT point an it has to be filed in flight plan. Osijek Approach will hand you over to Belgrade Approach 5 NM east of PEROT and you should be more-less precise reporting it.
It has for long been known that many eastern european countries want VFR flight plans to be filed along the airways and that they want the actual FIR crossings to take place via those waypoints located directly on the FIR border. Exceptions may apply.
If you’re flying down that way, I would recommend stopping off at Dubrovnik and spending some time looking around the old walled city – flew down there in June flying via Pula and Adria 1, very enjoyable indeed……
Bit of thread drift, but might be of interest:
Portugal is another country that insists on VFR traffic to enter/exit its FIR via defined points. They are published in their AIP, and IIRC, correspond to IFR waypoints along the FIR boundary.
