I'm going a little nuts trying to figure out what size duffel to choose for a 12-day African safari. I like the Big Haul because it folds into its own carry bag. I'm spending a week in England following my safari so I thought i might squeeze the duffel into my regular wheelaboard, but I'm not sure there will enough room for clothing! Also, are there any duffels that have a slip-sleeve to be able to attach it easily to wheeled luggage? Thanks for your help.