i have some of those powder river panels, not sure the length, but they are pretty long. anyway i have a few issues with them. one, the bottoms under the pipe parts of the panel are open and the wasps love to nest in them. two, they are just too heavy for me to move by myself without busting a gut. and three, they sink down into my sand too easily and therefor are impossible to swing open without dissassembling if they sit in one spot for very long. i put boards down under them to keep them from settling but they still work their way off and dig into the ground. if you dont need heavy duty panels for heavy duty cows i get something light assuming you dont have jumpers.