Lots of folks use the thumb tacks through the screen wire. The zip ties work also. One other idea is to put eye-hooks through the top frame and hang plastic chains down them. then use cup-hooks, or zip ties to attach them to the chain. That keeps the branches from stretching the side screening. How about another back board in the new cage and mount the branches on it? There's a dozen different ways you could do this. Let's see some pictures when you decide. Good luck!