I'd like to use my ramp as a patio. Is it safe to just put some jacks under the rubber bumpers? I load 980lbs bikes with that ramp so it should hold 3 or 4 adults, no?
I think if I was going to do that I'd run a 2x with carpet or something on it to prevent scratching, across the door from one jack to another just to give the middle a little support. I would also run it across about 2ft or so from the end and not all the way out to the rubber bumpers.
if you can find the structure you should be fine. Like you said heavy bikes roll up it supported only by the lip/bumpers and the hinge. You should be fine for 3-4 adults, as long as they're "normal" size.
The ramps that come from the factory, with the patio option, is rated for 1500 pounds when used as a patio. The patio/ramp door has a sheet of metal covering the plywood to aid in support as a patio.