If you are absolutely careful to get each panel "Exactly" the same as it's opposite panel, and keep all the edges even... ?? You can't possibly make it crooked..

When beveling your edges, just bevel about half of the inside edge off and leave some. The bevels are different all over the boat and basically all the bevels are for is to keep the edges in place when pulling the panels together.
You only need a small flat edge to keep them from sliding. If you bevel too much, you could create gaps and alter panel shapes when pulling them together.

If I remember correctly, there WAS some mention of using a level in one thread some time ago, but I think that would only work if your boat is totally locked into position, and with a S & G it won't be. A better idea, if you are worried about it being twisted would be to take 3 or 4 sticks and lay them across the gunnal/sheer from end to end and then site down the length of the boat and see how the sticks line up. ??

I wouldn't worry too much about it though.. as was mentioned, you will "See" any serious flaws while you are pulling the panels together.... take it slow, twist the wires a couple turns at a time, check the alignment, twist a little more... and so on. I undid and redid my Rob-Roy twice and found that getting all the edges close ( 1/8" ) and then bringing the ends together first worked the best.

Rehd