Garage door spring is too long and weak. Ok if you want spring running half way across your trailer like the yellow Gator springs. Ive made two of these. One for 12 foot Lone Wolf and last 16 foot Larimore trailer. Last one been on over 5 years. I can raise the gate off the ground with my foot, catch it with my hand and never have to bend over. Adjust your location point by using a chain held temporaily where you want it. Moving the chain hook on the spring and location point will tell you where you need to weld your spring older in order to take weight off gate and not break spring.
I just noticed i have some really nice shoes on in that photo. Lol