How strict is Tauck on using the Tauck issued bags? Or main suitcases (Briggs and Riley) are pretty much the same size as the Tauck bags which will be a real pain to have to pack in our suitcases which we always carry on planes. We could even just use on of our suitcases for the Nepal portion if it's a problem. In other words, we'd like to just use our own suitcases and forego the Tauck issued ones. Possible?