Austin to the rail camp horse race rules
The road between Austin and Fredericksburg lies along a route that was first best for big herds of cattle, and then later refined for travel by wagon. And then, further refined for travel by swift stage coach. But shuffling herds of four-legged cattle and four-wheeled wooden vehicles aren't comparable to the nimbleness of a four-legged coyote, deer, antelope, or horse. Even a horse with a rider.
If William and DT choose to race from Austin to the rail construction camp, here are the rules.
If you choose to just run with no Riding skill rolls, per the rules it would be a tie. William's horse has Strength 24, and DT's 23. Logically, in a long race, William's horse should edge out DT's. But to stick to the rules as written and not get overly complicated, let's say that William's horse just has the equivalent of an extra HP if it takes damage.
The riders can instead choose to get off of the wagons road and take shortcuts. If they succeed at a riding roll, they shave the listed amount of time off of the total trip. If they fail, they add the listed amount of time to the trip. The figures indicate adding or subtracting to the Riding score. For example, Joe's Riding is 9, and the modifier is -2. He needs a 7 or lower to succeed. The riders can choose to try or skip any of the shortcut opportunities.
There's no chance of injury to the horses or the riders for this race.
Riding check opportunities
1) Leave the wagon road at the bend and jump a little ditch: +/-0 to Skill score. Success, save 1 minute. Fail, add 1 minute.
2) Skip the little wagon bridge and jump a gully 6 feet across: -1. Success, save 3 minutes. Fail, add 2 minutes.
3) Avoid a curve below a rise and go right over it instead: -1. Success, 3 minutes. Fail, 5 minutes. (It takes a while to pick out a good route back to the road on the other side).
4) Jump a wire fence (and trespass): -4. Success, 5 minutes. Fail, 7 minutes.
5) Cross the little stream without watering your horse, push on to the camp: -3. Success, 4 minutes. Fail, 6 minutes.
Since it's PBP, I suppose we should state all five actions and do all rolls at once. But... since the story will move forward in time, no matter what the outcome of this friendly competition is, optionally we can treat it like an ongoing side tactical mini-game. Both players post for 1), then based on the results, post for 2), and so on until you reach the camp. It's up to you guys to do one or the other, or none. Whatever's doable and fun.
William is down for the race. Let’s do this! See you at the finish line! . He doesn’t have the horseback riding, but has a coordination of 18. I’m away from my rule book right now, so that’ll work out as it works out. 
