220km in 10 hours (with 2000m of climbing) and 160km in 5:45 on a flat bar that weighs 14kg loaded fast enough for you? Way under the time limit.
Mitchellon country and gravel (or a similar one). They have little or no flat protectipn but rolling resistence is mininal at speeds up to 60kmh at which point I have luttle desire to go faster anyway.