When I had a cargo trailer I used pet taxi style coops and other coops/cages to transport my Ameraucana chickens to shows for exhibition. I've sold the trailer and decided to only show as many birds as I can get in the bed of my pickup truck under the tonneau cover. To maximize the space I designed and built custom coops. Most have a divider, so they hold 2 birds ( 2 hole). They all have tops that slide open. The frames are 2x2" and 2x4" lumber, but 1x2" and 1x4" would make them much lighter. The bottoms are 1/4" plywood and the rest is perorated plastic, so there is plenty of ventilation.
These give me 22 holes, with up to 12 being big enough large fowl Ameraucanas. Some of the bantam coops are longer than others to allow extra room for the long tails on males.