You could also use some whoopie slings and use them as stabilizers. For example, tie two around the top tube with a lark's head. One to each side. Then tighten to keep upright. Or, if you know the trucker's hitch, that might be a better choice for this. Maybe use two more, one around the bars and the seat post for front and back. Of course, you can use more to make it very stable.