I think you need to call them and see what their maximum weight/rack capacity. They used to advertise their racks (the ones we have) could hold four bikes, and now they advertise three bikes. I believe the change was because of the many heavy downhill, fat tire, e-bikes , etc. We carry 4 bikes all the time with ours, but our bikes are on the lighter side. They do advertise a heavy duty model can hold 4 bikes. Maybe that option can hold five lighter bikes? Zero regrets on the cost and function of the rack.

I think the change was primarily made because 4 (heavy) bikes on a light duty (1 1/4") hitch could overwhelm the hitch. With the 2" (class III?) more capacity is guaranteed.

1up probably has a max capacity of 4 listed, but the modular design means you can bolt 10 trays together if you want to. If you want to put 5 bikes on, make sure your trailer hitch and vehicle are made for serious towing and double check all the aspects of your hitch capacity. You'll end up with a pretty long arm swinging around on the back and it probably isn't a good idea to go against the manufacturer's advice.

Presumably you're only going to be hauling 5 bikes on a infrequent basis, I would give some thought to putting two on the roof.