Let me sum it : I ask a guard, and he told me that there was nothing against it in the rules, but he didn't know : we should give try ! I insisted : Imy friends will come from foreign countries, I needed a real answer, He just told me again to give a try on the 26th !
He just didn't seem to give a damn.
We'll have to go dressed up and argue of our good will if someone forbide it. And really, if it' is impossible, we'd have the alternative to change up in your hotel room (my own flat is really far from the museum.)