that's good if the AB are not underlayed.
if so..don't bet the AB.
do
AB/C C/AB. If you cant' see the C in the winner circle...don't bet.
IMHO.
if the AB are underlayed it is a loser even if you cash.
you could also work with 4 horses with 2 chalkers by not playing them together
Let's say A and B exacta is underlayed.
Play:
AB/CD
CD/ABCD
$10.
A lot of times I will weight it having more on the AB/CD and also play a triple.
I've had good success with this in very contentious races with large fields and good prices. Some races you may never touch become great betting opps.
Now, if you can just figure out who A B C and D should be.