Unfortunately I do have to remove the seat stem off my bike ( Size 56 ), but my wifes bike ( Size 52 ) fits in without removing the seat stem by tilting it to clear the rear opening. With the seat stem out my bike rolls right in without tilting. Fortunately 80% of my training and group rides I ride to from my house. This was mainly designed for highway driving with the bikes. With two bikes on a hitch mount I loose about 3-4mpg, with 4 bike on a hitch mount I loose 6-8mpg.
4 Bike Rack (The 2 Bike Rack on the Subi is the same rack I use when I just need to take two bikes ):
-Jason