As a college graduation gift for my overachieving niece, my husband and I are planning a family trip to France and Italy next year. Niece's Dad, my beloved brother in law, is compassionate and hilariously funny, and will be more than welcome. The only trouble is he is a massive overpacker. Last spring he and his girlfriend were delayed by more than two days when travel plans snafu-ed, as they do, and he was unable to be flexible due to his luggage. He packs like he has porters: his whole wardrobe, mountains of shoes, the kitchen sink.
BIL's rationalization is that he sweats profusely and must change clothes during the day. I have pointed out that Europe has laundry and we can do it every other day without hassle.
My husband and I travel with one carry-on each and love it. We don't want to spend our trip moving slowly because of BIL's dozens of shirts.
What are some strategies to persuade BIL to downsize his luggage in the interests of a smoother trip?