This is the setup I've used on race bikes. Weight is limited to 20 pounds, and you have to use an alloy or steel seatpost (not carbon). Topeak MTX rack with DX-P trunkbag with zip-out panniers. It's a cools system, although not cheap. It travels easily from your home to Europe, etc., having to carry it on the plane and trains. It literally slides off the rack when you're at your destination with the click of a button, and it has a nice handle atop the trunk for easy carrying.

Only downside is cost -- about $200 all in (rack, trunk, raincover, side stiffeners for panniers, confiscatory gov't. tax .)