I had a look at your route and am curious: how did you get clearance for your rally from the Dutch, Belgian and German police?
I ask as I have done the Gumball3000 rally (www.gumball3000.com) a couple of times and currently help (on a strictly amateur basis) the CarbonBlack rally (www.carbonblack.com). Police in the three countries I mentioned hate rallies.
The Dutch will arrest any driver exceeding the speed limit (no matter how small the margin) and impound cars. The Belgiums close motorways (diverting the traffic through petrol stations manned by 50+ police) and search all vehicles for illegal devices (radar detectors, laser jammers, police lights and sirens, etc), while doing a 100% document check (only originals accepted) and brethaliser test. The Germans simply arrest all drivers and impound the cars (no matter that no law has been broken). Last year they impounded all the cars and arrested all the drivers and kept them in laybys for a couple of hours before escorting everyone to the airport (in slow convoy) and held them there for 36 hours (time enough the police believed (correctly) to ruin the rally.
If you negotiate with every single police municipality in Germany that you will be passing through then sometimes it is possible to get tacit clearance (i.e. they will not go out of their way to arrest you). Otherwise you will face a barrage of angry gestapo in umarked BMW M5s and Audi R6s after you (I have been arrested and then released 5 times (thanks mainly to possession of a diplomatic passport)).
The Austrian police hate rallies but obey the law: all they do is put a speed trap every other kilometer on their motorways (and fines start at 300euros; largest one given to a friend on a rally was 1,500 - payable on the spot via credit card or cash).
The Hungarians currently tolerate rallys, but have installed a total of 8 speed cameras on the Vienna-Budapest motorway (all set at 138kmph). You should be ok with these unless you are going at a silly speed (that triggers an automated alarm and the police will catch you at the border). If you enter Slovakia then watch out for Audi RS4s: they have 6 patrolling the motorways between Bratislava, Czech, Austria and Hungary. The Czechs have an annoying habit of placing a speed trap in every 3rd village and on the motorways having the ambush unit placed out of view (on a small road overlooking the motorway, hidden behind bushes etc) and then a stop group a couple of km later. They also patrol in Skoda Octavia RSs and a couple of Lagunas (unmarked as well as overt).
If your rally is small (less than 15-20 cars) and without any livery (no numbers, badges, decals, etc) then you will probably have no problems. If fully stickered up, then I will read about you in the local papers!
Thanks for that info dread, the idea of the rally is to get a heap of shite chaved up car across europe, i doubt any speed limit will be broken, and it will be up to the indivdual teams to stay within the law.
I will post your advice on the website, please inform me of any thing else that you might think of.