The tank diagnosis sounds correct, heating up in the sun and pressurizing the fuel past the shut off valve.
There are one or two aspects of MB's which seem to fall into a 'Bermuda Triangle' when it comes to detailed coverage
1. Atmospheric pressure-dependent full-load stop (ADA)
2. Metric v imperial flares on brake lines
3. Fuel tank vents/filters.
I think one of the reasons is they vary from country to country and possibly state to state making direct comparison difficult.
The tank vent for my W210 is located inside the front nearside wing, again this may vary for each model/year ect.. best bet is to physically trace it from source.
It's on my to-do list for both cars when the weather improves here.