We had a little SNAFU with the low tunnels, as we'd ordered all of our row cover 83" wide (to cover a full 6' bed with room for plants to grow). Unfortunately when you drape that 83" over a 6' hoop that's got 12" in the ground on either end, you have about 3 feet of slack. We really didn't want to punch holes through the middle of the stuff (it's almost $200 a bolt), but we also need it to be taught so the hoops are well-formed and don't press on the plants or blow away in the wind.
After much gnashing of teeth, we ended up shoveling in the entire row. We may end up cutting the remainder of the bolt down to the right size and writing the difference off as a the cost of learning, or we may keep shoveling. Shoveling soil works better than the alternatives (sand bags or plastic spikes) but it's very, very time-consuming.