Yeah, 20-3 can be a chore.

If one of your squads is much faster than the others you can leave them by themselves in the top camp. That forces them to take the long way to the finish line, although it may also mean they don't get to the pest fight just before the boss. When taking this approach put all four of the remaining squads in the leftmost camp then hope enough of those squads head southeast instead of south from the random tile. The center camp can be used if you have a super slow squad, or a squad strong enough to win one pest fight but not two. Even then, if the random tile directs them towards the two pest nests instead of the pest fight it ruins the point of putting the squad in that center camp.

Putting two squads in the top camp can work too as long as the faster of the two squads hits the arrow tile first so that they take the longer path. With this approach it's still best to put the remaining squads in the leftmost camp.