I have a ladder rack but only use it for two of the kids bikes. My ladder is too close to the side of the trailer so adult bikes would stick out to the curb side too much. I carry two adult bikes on a bumper mount rack that has two mounting points on the back bumper.
I'll have to figure something else out for this year. My youngest, my daughter, her bike was always small enough to just set inside the 5er. But now shehas a bigger one that will have to mount outside. Plus my oldest son is nowinto an adult size bike so will need to mount some place other than the ladder. I am looking at a front mounted receiver for my truck to use for a 4 bike set up. My second son will be on an adult size bike in the next year or so anyway. Don't know what I'll do in about 4 years when I'll have to carry 5 adult size bikes....
2005 CF29RE 04 Ford F250 crew 6.0 P/stroke FX-4.
(pic coming soon!)