I had three different contracts with ferrying a total of 14 tourists to various combinations of landing/orbiting Minmus or the Mun. I found it saved mass to just strap down 16 seats in two service bays (1.4t) than to use multiple hitchhiker modules (2.07t for 4 pax) or multiple trips. So all 14 tourists are now going to Minmus and the Mun.