Ok...first of all, if the top edge of the receiver hole is only about 7" off the ground, that is an inch or two lower than most, but still just fine. Get one like pictured in this link from Northern Tool. You can insert it "upside down" and pick up about 4" of ball height. If that is more than you need, remove the ball and insert it in "right side up" and re-install the ball. Is isn't critical that the trailer sit perfect level. It's fine if it sits a little nose high.