Many times we shoot combinations softer than our usual stroke with the idea in mind of controlling the first ball. If the balls are close together, there will be cling and we will undercut the second ball. If there is a little distance between balls, the first ball willl develop a little forward roll which will lessen the throw effect somewhat.Maybe it's just the way that I see them, so I admit I could be wrong, but I seem to have read somewhere...............and when I've had success, I aim to cut the 2nd ball thinner than usual because I feel as if for some reason in combos there seems to be more cling/throw issues than a normal 'true' cut with the CB. Again, it may just be the way that I see 'em, but although I don't like to combo, this formula has worked for me.
dave
Hitting the shot with a firm hit, if possible, will help eliminate under cutting the second ball, too. Straight pool is a great tool to learn combination shots.
Best,
Mike