I bought a 6x12 from Northern tool. Flat front. I rigged it for camping too, with batteries, lights, etc. It can not hold 4 full size bikes side-by-side. It holds 3 comfortably. The front of mine has about 3 feet reserved for tupperware, tool chest, generator, etc. You could use that space for the bikes and have room for a 4th bike facing backwards. It pulls very well behind a 5.3L suburban. I would not go any smaller. I added electric brakes, a must-have item. If I had to do it all over again I would get the dual axle 7x12 or 14, but you could make it work.