Years ago I would take my cap off in the summer time.
I simply used two stout ropes suspended from the floor joists in the barn in which I parked.
Back the truck in, remove mounting hardware.
Carry one end of the rope into the bed with me when I climbed in. Used my back to gently lift the cap an inch or so along one side of the bed rail until I got the rope all the way to the front of the cap. Repeat with the other side and the other rope.
Then I 'd just pull on the rope gently until the cap was clear from the bed in the front and again in the rear, just tying it off temporarily until I pulled the truck out and then hoisted the cap until it nearly touched the joists.
It wouldn't go up straight because of the friction of the rope underneath the cap side walls, but I'd just keep evening it out as I went.
A little bit cumbersome, but I only did it 2x per year so I couldn't see investing bucks in pulleys and whatnot.