TJ, don't think I would change the closed angle of the shackle to gain height. I think it will cause them to bounce open and closed to easily. Going up steep stuff they sometime start to clap with to much throttle and limited traction.
I went with a center limiting strap that stops the axle just before they open, to prevent them from unloading on steep decents. But it still allows one side or the other to fully extend. My measurements won't work for you due to a different leaf pack. starting point for max shock length around 27.5" to 29.5". you'll gain max extension relocating shock mounts.
I was to late to reinforce mine so I'll be buying new ones