+1 to just using more conductors. Yes, connectors rated for power are available and are good choices for durability, making sure the right thing is plugged in and with the right polarity, and all sorts of other reasons, for just testing things out on something you're going to be using yourself, adding extra conductors means sharing the current (also a concern with the wires used to connect 2.54mm pins) and reducing contact resistance.
If you have a place to drill a hole or something, you can also just use a decent sized solid core wire (maybe 20 gauge?) and run a little jumper to a different connector - something like your standard barrel jack would handle that current and could be mounted in just a hole if you've got the wire jumpers.
If this is going to be a product made in the thousands and this connector is available to the end user, you're probably much better off finding a different connector, but on the small scale, there are a bunch of potential workable options depending on your constraints (Like if you only have one pin for power and ground and can't add more, the jumpers to a different connector is probably the way to go).