Ok so I'm drawing up some plans to build a shooting bench for my farm in OK. I'll have seats on both sides to accommodate both left and right hand shooters. The cross section (widest part) is 7' wide. The entire length is 7' long so people can go prone on it. The long part of the T is 3' wide. The seats will be 17" square. Is this a good start? How should I brace this because I want it to be mobile. Any ideas? Thoughts? Suggestions?