Just picked up my Tarpon 120. Trying to rig the milk crate for the back and it seems a little to big. Milk crate measures 13"x14". Is this what other folks have or are there truly 13"x13" crates out there that i just can not seem to find. Also any tips on how anyone has it secured once in would be great or other outfitting tips. I am just starting to do the outfitting. I have paddled for years but this is my first SOT and first kayak that will be primarily for fishing. Be gentle!