The plans give very exact dimensions (and there are several sites that use these same dimensions). Each arm is a v that is 7 inches long and 3 inches apart at the end. there are 4 sets of v's that are 5 3/4 inch apart. The only bare copper lowes had in stock was pretty big (like 8ga) and would have cost 15-20$. I got 12ga for about 2$ but it was not available bare.

So it would help to strip off all the wire insulation?