Mississippi confusion...

Just had a game of Mississippi Queen, the Game of the Year from 1997. In the game, turn order is determined by the player "furthest ahead". In most cases this is easy enough to determine. However, there are moments where the river snakes in a semi-circle and then it is really hard to determine. One player can be farther back by a number of spaces but still be ahead according to the rules and vice-versa. The rules translation doesn't help much at all. Anyone have the same problem? Any suggestions?