There is also the issue of the design - I'm assuming you are looking at the metal panels that link together, since you said 2 60' pens. Part of what holds them up is the angle formed by joints where the panels come together. If you try to make a straight line rather than a curve, you may find the pen unstable on that side, which means it may lean inward or outward rather than standing up straight. Combined with unlevel ground, that may mean the panels get bent and twisted; you may need some additional means of support to keep the panels straight.
