You should be able to if you stagger them. The strapless trailer stands (ie PitBull's system) would make life a heck of alot easier. Make sure you check the weight rating of the trailer and the tires to make sure you're not overloading the axles and rubber. (If it's a 2 axle trailer, 4 bikes should be fine)
I hauled 3 in a 7X12 non vee nose and it was a tight fit. 1 in the center at the front strapped down and 2 on the sides at the back on strapless stands facing backward.
I got 4 + all gear into a 7x12 v-nose with a closet, sink refrigerator and a porta potty up front. It was tight, but its definitely possible. 900 miles each way to jennings, nothing touched.
Pitbull flat out rocks. I got three mounting plates in my 7x12 and have lots of room left over for all the other stuff I gotta haul around. Can't go wrong with Pitbull.