I'll second buddroyce; 3 parallel should be fine. You'll probably have to crank the claw down almost all the way, but you should be able to get it. If it's not quite there, going to an arrow config will add a little more tension.
I tried it with the 3 springs and unfortunately it just wasn't enough. I wasn't able to get the right springs so I had to use a lower gauge (10 13 17 42 52 68 ), It was the little ****ers causing the problem.