A US30 with 2US 20's would make for a bulky bundle. My 30 lays lengthwise on the rear seat with a US 10 on each side. I slide it a bit to the rear to make room for my backrest and the rear of the 30 covers 1/3 to 1/2 of the OEM luggage rack. I can carry 6 - 7 days worth of T-shirts, underwear, & socks in the 30 with my Dop Kit. Other incidentals go in the 10's.