Hi Joe,
I am using 15t in the front and 40t in the back. I have been looking for cheap aluminum sheeting but even for a 3 by 8 ft of 26 or 28 guage its $50+ from the local recycle yard. I might go L&S route and cover in election signs.
Going up in the front is a better idea than going down in the back so you don't have to cut out links in the chain.
Look forward to collaborating w/you on beating the ninjas
.