Not having or using a "gantry crane", my opinion is not the most useful. However, having worked in the steel mills and foundries in this area, I do have a good concept of what a structure will take.
With any Harbor Freight device, I have a rule of thumb that has held up well for me over the years. I assume any device of their's is usable at
one half its' rated capacity. A device rated at one ton will lift one ton,
one time. Then be useless beyond a place for hanging stuff. Used at half capacity, it will hold up pretty good for an amateur. An example being the sheet rock panel jack. It'll do 3/4" plywood, but is pushing the limits.
The same thoughts apply to any hoist made overseas. The one from "palletforks" is rated at two tons. Used as a one ton hoist, you would be well enough off. With a slight margin for error if it ever came up. That is the key to any lifting equipment, a good safety margin. A 100% margin is minimal. From an industrial perspective, three or four times is comfortable, five or more would be even better. HF stuff is rated in absolutes, no safety margin.
I have used wooden ramps a number of times for unloading things over the years, usually with
little or no margin of error. But the wood is then used as "scab" lumber, nothing structural. The thoughts of trebling the timbers given above is right on point. The key is the grade of lumber used. Spruce or fir is trim lumber, not structural. Pine or oak would give better service.
A truss configuration would give better service than a solid. That a given in wood or steel. A roof truss of great span, 30 ft or more, when used for a small 10 ft beam would hold a pretty good weight. I'm rambling now, designing by remote. A bad move at the best of times.
Bill Hudson