Assuming this to be the Eurotunnel train ?
We just went backwards and forward recently on the lower deck in the Aero Coupe which should be the same 4.8L exposed sump as your S5. No concerns re the grounding, more concerned over the rims on the edges of the carriage. We did some amazing places on the way up and down if you are interested.
CHÂTEAU D'ÉTOGES - Epernay
Relais & Châteaux L'Assiette Champenoise, Tinqueux, Reims
Both have amazing hotels and even more amazing food.
Put the address for Borghi in Milan in your sat-nav in case anything burps.
If you are going that far down Lake Como is beautiful but the roads are thin and seem to have a random surfacing element!
Tight hairpins. Rear wheel steering is available on mine based on experience. Manual hold on second or third seems to enable it.
