My $10 trailer gate lift, struts
First of all this wasn't my idea, there are others on the board that have done this to their gates.
I went to the U-Pull-It and picked up two struts and strut mounts from a 99 Windstar. They are the strongest I could find in my quick web search, they are rated at 163 pounds each. The struts were $4 and change each. I built the brackets out of steel I had, and spot welded everything together to try it out. I think the struts may be too strong. You actually have to push the gate down. Lifting it is very easy.
Since these photos I welded the brackets on and painted them black. I also flipped the struts over so that if they get wet, it won't run down into the cylinder.
I am not sure this is a perfect system, we will have to see how they stand the test of time. When the strut is on a car, it is inside, and protected from the weather. I do park my trailer inside, but when it's on the road the struts will see dust, dirt and moisture.
I also think I need to move the struts out about an inch on my lower bracket, I think if we park high, and the gate goes really low, we will bottom the strut out in the cylinder. For now I am leaving the lower brackets long, and once I am happy with the positioning of the lower strut mount I will trim them off and round the corners.