The best I can do for you is tell you that when City played away in switzerland at lausanne, we had no trouble with flags and drums (or was it bodhrans).
I've seen a few games in switzerland and Drums, large Flags and even flares are common place, i wouldn't forsee a problem, in general the swiss are laid back, understand the difference between a drumstick and a weapon and as long as you look like you can control what you bring in (i.e. aren't steaming drunk) you won't have a problem.
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