"I used two each gas springs rated at 20 pounds each. (No, my canopy does not weigh 40 pounds.)"
This is a very good point. You don't size the strut to the actual weight of the item you are trying to lift, it all depends on the geometry of your design. Last year before Sun-n-Fun I built a car top carrier for my generator out of 1/2" foam and split it so I could raise the top to run the generator without having to relocate anything. The lid didn't weigh five pounds, but due to the geometry of my design, my original 20 lb strut wouldn't even crack the lid open. To get it to work properly this year I will be replacing the single 120 lb cylinder with two 90 lb cylinders. Most folks won't need anything as strong as this but I was space limited so had to use very short cylinders. For canopies I would suggest copying Langford's design and if you have any problem finding cylinders McMaster Carr is an excellent source and they have an assortment of mounting options and fittings that can be used at each end. Stephen Teate Paradise, Texas
