The thicker the stack, the slower the cut. You were using a 2/0 blade, which is a relatively small blade. You probably had to retension it a couple of times. You could have used a bigger blade to achieve speed but you would have had a bigger kurf. I use 2/0 blades all the time and it takes longer to achieve the cut with thicker wood. Try very hard not to push, it will distort your cut. I've never thought to double the pattern, I will have to give that a try. Just be aware, when you try that same blade with thinner stock, it's off to the races! It will go so fast you may have trouble controlling where you are going. Give it a try.