Riding on gravel can be challenging. Sometimes the front tire will be knocked off track by deep gravel (similar to when trying to plow through deep sand), so steering occasionally requires body english and upper body strength. I would put the biggest (i.e., fattest) tire on the front so that you have maximum flotation and the wheel has more momentum to resist being knocked off track. Also, try to read the trail ahead and avoid those ares that have built up piles of gravel like downward sloping sides of curves. Braking can be iffy, especially on curves. Always be prepared to use body english when braking so that you can control the inevitable skiding. Generally, riding on gravel requires staying alert and being able to "manhandle" the bike to compensate for the surface being so unpredictable.