The poles for my REI Half Dome 2 measure 17.5" long. This is for a tent with a floor size of 90"x54". I'm 6'1" tall and the tent is plenty long for me. The whole tent, rolled up around the poles and in the stuff sack, measures 20" long. I strap it across my rear rack like this (tent is the bottom right of the stack of the first picture and bottom left of the second). Ignore the laundry drying in the first picture:





It doesn't stick out appreciably beyond the width of my panniers. If it stuck out a little more, it wouldn't bother me. I like to present a wide profile to cars passing me. I strap the tent, sleeping bag, sleeping mat, and pillow (I sleep well) to my rack with nylon cinch straps. I cinch them down tightly and they don't move a bit while I'm riding, unlike loads attached with bungee cords.